CVE-2026-58399
HighCVSS 8.7Exploitation Probability (EPSS)
Low risk42th percentile — higher than 42% of all known CVEs
Summary
A vulnerability in the @acastellon/auth authentication system for microservices allows an unauthenticated attacker to bypass token validation via crafted auth-user and Host HTTP headers. The issue affects validateToken() in versions prior to 2.3.0.
Risk Assessment
An attacker can gain unauthorized access to protected microservices by impersonating a trusted client (service-brother), leading to data confidentiality and integrity breaches.
Recommendation
Immediately upgrade @acastellon/auth to version 2.3.0 or later, which includes a fix that prevents token validation bypass.
Original NVD description (English source)
@acastellon/auth is an authentication control system for microservices. Versions prior to 2.3.0 appear 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. A fix has been implemented in v2.3.0.