Vulnerability in Traefik
CVE-2026-88011
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (36.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 36.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Traefik — versions < 2.11.56, >= 3.0.0, < 3.7.12
Weakness classification (CWE)
References
- github.com/traefik/traefik/security/advisories/GHSA-rf44-j88r-hh8c (Patch, Vendor Advisory)
- github.com/traefik/traefik/pull/13720 (Patch, Issue Tracking)
- github.com/traefik/traefik/commit/0331801c72329e0eaeb850e53ccce87c57fbecf8 (Patch)
- github.com/traefik/traefik/releases/tag/v2.11.56 (Release Notes)
- github.com/traefik/traefik/releases/tag/v3.7.12 (Release Notes)
Frequently asked questions
- What is CVE-2026-88011?
- CVE-2026-88011 is a high-severity vulnerability in Traefik, classified under Authentication Bypass by Spoofing. CVSS score: 8.1/10. Published 2026-09-10.
- How severe is CVE-2026-88011?
- High severity. CVSS v3 base score is 8.1 out of 10.