@acastellon/auth: Authentication bypass via spoofable headers in validateToken()

@acastellon/auth v2.2.0 appears to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers. The validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP client: auth-user is a request header, and Host is also client-controlled. As a result, a remote unauthenticated attacker can send a request with crafted headers and bypass token validation before the normal legacy/JWT/OIDC validation logic runs. Impact: An attacker may be able to access routes protected by validateToken() without a valid token. In deployments where downstream services trust auth-user or is-* headers, this may also lead to privilege escalation. Affected package: @acastellon/auth v2.2.0 Affected code: auth.js, validateToken() The issue is related to the service-brother bypass and getHostName() check. Example request: ``` GET /protected HTTP/1.1 Host: <configured CNAME or hostname> auth-user: service-brother is-admin: true ``` Expected behavior: The request should require a valid authentication token. Actual behavior: The middleware calls next() before token validation. Fix implemented in v2.3.0+: Removed the spoofable bypass. Always sanitize incoming auth-user and is-* headers. Added mTLS client certificate based service auth (with optional TRUSTED_MTLS_SERVICES allowlist). Updated consumers (rest, graphql, dns-client) for mTLS support. Unit tests added for sanitization + mTLS path.

Source published

18 Jun 2026 17:22:47 UTC

Source modified

10 Sep 2026 03:51:08 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Publisher rating · CRITICAL