CVE-2026-25748
HIGHCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Lifecycle Timeline
2Description
authentik is an open-source identity provider. Prior to 2025.10.4 and 2025.12.4, with a malformed cookie it was possible to bypass authentication when using forward authentication in the authentik Proxy Provider when used in conjunction with Traefik or Caddy as reverse proxy. When a malicious cookie was used, none of the authentik-specific X-Authentik-* headers were set which depending on application can grant access to an attacker. authentik 2025.10.4 and 2025.12.4 fix this issue.
Analysis
Authentik Proxy Provider allows authentication bypass through malformed cookies when deployed with Traefik or Caddy as a reverse proxy, enabling attackers to access protected applications by circumventing forward authentication checks. The vulnerability stems from improper cookie validation that prevents the setting of required authentik-specific X-Authentik-* headers, potentially granting unauthorized access depending on the backend application's configuration. …
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Remediation
Within 24 hours: Identify all instances of authentik Proxy Provider deployed with Traefik or Caddy and document them; assess whether any are protecting production systems. Within 7 days: Implement compensating controls (WAF cookie validation rules, restrict cookie size/format, network segmentation) and monitor authentication logs for suspicious cookie patterns. …
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