CVE-2026-88004 Traefik entrypoint header-name sanitization bypassed via request trailers
Attackers can bypass header sanitization in Traefik by using HTTP trailers, potentially spoofing identity or routing data to backend services.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-88004?
CVE-2026-88004 is a high-severity vulnerability in Traefik Traefik, published on 10 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-88004?
5 open source packages ship an affected version, including github.com/traefik/traefik/v3, github.com/traefik/traefik and github.com/traefik/traefik/v2. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/traefik/traefik/v3 Go | From 3.2.0 | 3.7.13 |
github.com/traefik/traefik/v3 Go | From 3.2.0 | 3.7.13 |
github.com/traefik/traefik/v3 Go | From 3.2.0 | 3.7.13 |
github.com/traefik/traefik Go | All versions | None |
github.com/traefik/traefik/v2 Go | All versions | None |
Products include Traefik Traefik.
How do I fix CVE-2026-88004?
Upgrade github.com/traefik/traefik/v3 to 3.7.13 or later.
Is CVE-2026-88004 being exploited?
There is no known exploitation of CVE-2026-88004 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-15c1-824f-cb33, GHSA-v67p-phpq-fc8x, GO-2026-6467, MINI-5q89-8744-cwx7, MINI-xc5m-jqv5-mq57.