CVE-2026-85595

Traefik's digestAuth middleware mishandles unknown usernames: instead of rejecting the request, it derives a digest from an empty secret, which lets attackers compute a valid digest response using completely arbitrary credentials. An attacker who can reach any route protected by digestAuth therefore authenticates without knowing a valid username or password. Successful bypass grants unauthenticated access to whatever backend services those routes protect, such as internal APIs, dashboards, or admin panels. Only Traefik deployments that actually configure the digestAuth middleware are affected, running versions in the 2.x line before v2.11.55 or versions v3.0.0 through v3.7.10. No exploitation has been observed: there is no public proof-of-concept, the flaw is not in CISA KEV, and EPSS estimates a 0.4% probability of exploitation within 30 days.

What to do: Upgrade to Traefik v2.11.55 or later on the 2.x line and to a 3.x release newer than v3.7.10. Audit configurations for digestAuth middleware usage and, as an interim mitigation, switch affected routes to basicAuth or another authentication mechanism or restrict their network exposure. Since no public PoC exists yet, prioritize internet-facing Traefik instances that expose digestAuth-protected routes.