Vulnerability in Traefik
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.005 (39.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Traefik — versions >= 3.2.0, < 3.7.13
Weakness classification (CWE)
References
- github.com/traefik/traefik/security/advisories/GHSA-v67p-phpq-fc8x (Patch, Vendor Advisory)
- github.com/traefik/traefik/pull/13822 (Patch, Issue Tracking)
- github.com/traefik/traefik/commit/55bbda4f65e0f9c533c870983a767a7081126db7 (Patch)
- github.com/traefik/traefik/releases/tag/v3.7.13 (Release Notes)
Frequently asked questions
- What is CVE-2026-88004?
- CVE-2026-88004 is a high-severity vulnerability in Traefik, classified under CWE-436. CVSS score: 7.4/10. Published 2026-09-10.
- How severe is CVE-2026-88004?
- High severity. CVSS v3 base score is 7.4 out of 10.