CVE-2026-88011 Traefik: ForwardAuth identity spoofing via dot-form header alias
Attackers can spoof identity headers in Traefik ForwardAuth setups if alias protection is disabled, allowing unauthorized access to backends.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-88011?
CVE-2026-88011 is a medium-severity authentication bypass vulnerability in Traefik Traefik, published on 10 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.
Weakness: CWE-290
Which versions are affected by CVE-2026-88011?
It affects 1 product.
Products include Traefik Traefik.
How do I fix CVE-2026-88011?
Upgrade to a fixed version.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-88011 being exploited?
There is no known exploitation of CVE-2026-88011 in the wild and no public exploit code.
Other vulnerabilities in Traefik Traefik
- CVE-2024-45410 HTTP client can remove the X-Forwarded headers in Traefik
- CVE-2026-88877 Traefik v3.7.0 Authentication Bypass via from-to-www-redirect
- CVE-2026-85595 Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth
- CVE-2026-88007 Traefik HTTP/3 Backend NTLM Connection Reuse
- CVE-2026-88009 Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging
Sources
Also known as ECHO-623a-37ca-7a37, MINI-3cm7-7494-jx7m, MINI-gqhr-g88j-q3jr, MINI-w2qc-rwf4-r9h4.