Executive brief
Traefik is a reverse proxy and load balancer widely used to route incoming traffic and enforce authentication policies. The digestAuth middleware—designed to verify user credentials—contains a critical flaw that allows attackers to completely bypass authentication without knowing any valid username or password. An unauthenticated attacker can make two simple HTTP requests to access any protected service, including the Traefik dashboard and admin APIs, compromising confidentiality and integrity of protected resources.
Technical details
The vulnerability is a cryptographic authentication bypass in the digestAuth middleware caused by improper secret handling (CWE-287). When a user is not found in the configured user list, the secretDigest function returns an empty string instead of signalling an error. The underlying go-http-auth library then uses this empty string as the HA1 hash value and proceeds with HTTP Digest validation. Since the attacker controls the username, nonce, cnonce, nc, qop, method, and URI parameters (or receives the nonce from the server), they can compute a valid digest response offline: MD5("" + ":" + nonce + ":" + ...). The middleware then accepts any non-empty username returned by the library, allowing arbitrary authentication bypass with no preconditions. Patches are available in v2.11.55 and v3.7.11.
Affected products
- Traefik Traefik before v2.11.55 and v3.0.0 through v3.7.10
Timeline
- 2026-08-21: disclosed: GitHub Security Advisory GHSA-5w68-77r2-r64c published
- 2026-09-04: patched: v2.11.55 and v3.7.11 released with patches