fix(http): validate the Mcp-Session-Id header#157
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Reject session-id headers longer than 128 bytes or outside a URL-safe charset with 400 before any allocation or map lookup, instead of taking the header at face value. Assisted-By: Claude Opus 4.7 <noreply@anthropic.com> Signed-off-by: Sergey Vilgelm <sergey@vilgelm.com>
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📌 Summary
The
Mcp-Session-Idrequest header was taken at face value, with no length or charset check, so an attacker could send very large headers to force allocations and map lookups. The header is now validated (length and URL-safe charset) before use; invalid values are rejected with400.🔍 Related Issues
✨ Changes Made
parse_session_id_headerwith a 128-byte cap and URL-safe charset check, shared across POST/GET/DELETE.400before any lookup.