Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth (traefik traefik)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.24 % · percentile 15 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Analyzed
Description
Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.
Weaknesses (CWE)
- CWE-178 — Improper Handling of Case Sensitivity
- CWE-290 — Authentication Bypass by Spoofing
- CWE-345 — Insufficient Verification of Data Authenticity
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | HIGH 7.8 | 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 | GitHub_M |
| CVSS 4.0 | HIGH 7.8 | 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 | NVD · security-advisories@github.com (Secondary) |
| CVSS 3.1 | CRITICAL 10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N | NVD · nvd@nist.gov (Primary) |
Advisories
- GHSA-x677-9fxg-v5c5 — Traefik: Incomplete fix for CVE-2026-33433 + CVE-2026-39858 cross-cohort: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth
- GO-2026-6211 — Traefik: Incomplete fix for CVE-2026-33433 + CVE-2026-39858 cross-cohort: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth in github.com/traefik/traefik
European references
- ENISA EUVD · EUVD-2026-41940
- GCVE · GCVE-0-2026-54763
CERT-FR advisories
- CERTFR-2026-AVI-0989 — Multiples vulnérabilités dans HPE Aruba Networking Private 5G Core · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0823 — Multiples vulnérabilités dans Traefik · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*< 2.11.51cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*≥ 3.0.0 < 3.6.22cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*≥ 3.7.0 < 3.7.6
Affected products
| Product | Versions |
|---|---|
| traefik · traefik | affected < 2.11.51 ; affected >= 3.0.0-beta1, < 3.6.22 ; affected >= 3.7.0-ea.1, < 3.7.6 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |