CVE-2026-88004
Traefik entrypoint header-name sanitization bypassed via request trailers
Impact
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
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/traefik/traefik/v3 | >= 3.2.0, < 3.7.13 | 3.7.13 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Traefik | Traefik | from 3.2.0 before 3.7.13 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-v67p-phpq-fc8x
- https://github.com/traefik/traefik/security/advisories/GHSA-v67p-phpq-fc8x
- https://nvd.nist.gov/vuln/detail/CVE-2026-88004
- https://github.com/traefik/traefik/pull/13822
- https://github.com/traefik/traefik/commit/55bbda4f65e0f9c533c870983a767a7081126db7
- https://github.com/traefik/traefik/releases/tag/v3.7.13