Vulnerability · Published Sep 10, 2026 · Assigned by GitHub_M
CVE-2026-88004Traefik entrypoint header-name sanitization bypassed via request trailers
High 7.0
In plain English
A high-severity security flaw in traefik from traefik. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Traefik is an open source HTTP reverse proxy and load balancer. From 3.2.0 until 3.7.13, Traefik entrypoint defenses aliasHeadersStrategy, underscoreHeadersStrategy, and forwardedHeaders inspect req.Header but not req.Trailer, allowing an unauthenticated client to submit an aliasing or trusted header name in an HTTP/1.1 chunked trailer or an HTTP/2 trailer. When the retry or buffering middleware reads the body before the reverse proxy clones the request, the attacker-controlled trailer value reaches a backend that merges trailers into the header namespace, bypassing the documented delete or reject behavior and potentially spoofing identity or forwarded routing data. This issue is fixed in 3.7.13.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/traefik/traefik | no fix listed | GO-2026-6467 |
| Go | github.com/traefik/traefik/v2 | no fix listed | GO-2026-6467 |
| Go | github.com/traefik/traefik/v3 | 3.7.13 | GHSA-v67p-phpq-fc8x |
| Go | github.com/traefik/traefik/v3 | 3.7.13 | GO-2026-6467 |
Affected products (as reported)
Weakness: CWE-436, CWE-807 · Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
References
- https://github.com/traefik/traefik/security/advisories/GHSA-v67p-phpq-fc8x x_refsource_CONFIRM
- https://github.com/traefik/traefik/pull/13822 x_refsource_MISC
- https://github.com/traefik/traefik/commit/55bbda4f65e0f9c533c870983a767a7081126db7 x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.7.13 x_refsource_MISC