CVE-2026-39858
10.0 CritiqueDescription
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only canonical header names (e.g., X-Forwarded-Proto) and does not strip or normalize alias variants that use underscores instead of dashes (e.g., X_Forwarded_Proto). These unsanitized alias headers are forwarded intact to the authentication backend. When the backend normalizes underscore and dash header forms equivalently, an attacker can inject spoofed trust context — such as a trusted scheme or host — through the alias headers and bypass authentication on protected routes without valid credentials. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.
Produits concernés
Scores CVSS
| Version | Score | Source | Vecteur |
|---|---|---|---|
| 4.0 | 7.8 Élevée | security-advisories@github.com | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| 3.1 | 10.0 Critique | nvd@nist.gov (NVD) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N |
| 3.1 | 8.2 Élevée | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N |
Faiblesses (CWE)
Références
- https://github.com/traefik/traefik/releases/tag/v2.11.43 ProductRelease Notes
- https://github.com/traefik/traefik/releases/tag/v3.6.14 ProductRelease Notes
- https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2 ProductRelease Notes
- https://github.com/traefik/traefik/security/advisories/GHSA-5m6w-wvh7-57vm ExploitMitigationPatchVendor Advisory
- https://access.redhat.com/errata/RHSA-2026:21772
- https://access.redhat.com/security/cve/CVE-2026-39858
- https://bugzilla.redhat.com/show_bug.cgi?id=2464234
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39858.json