CVE-2026-88004

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.

• CWE-436
• CWE-807

• https://github.com/traefik/traefik/commit/55bbda4f65e0f9c533c870983a767a7081126db7
• https://github.com/traefik/traefik/pull/13822
• https://github.com/traefik/traefik/releases/tag/v3.7.13
• https://github.com/traefik/traefik/security/advisories/GHSA-v67p-phpq-fc8x

Published

Sep 10, 2026

Last Modified

Sep 10, 2026

Status

Awaiting Analysis

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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