CVE-2026-39858
critical
CVSS v3
10.0
CVSS v2
—
VIR risk
10.0
Description
Traefik: Pre-authentication decision bypass due to forwarded alias spoofing
Predictions
Exploit likelihood
98%
Patch ETA
—
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Vendor advisory: security-advisories@github.com — https://github.com/traefik/traefik/security/advisories/GHSA-5m6w-wvh7-57vm
Vendor advisory: security-advisories@github.com — https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2
Vendor advisory: security-advisories@github.com — https://github.com/traefik/traefik/releases/tag/v3.6.14
Vendor advisory: security-advisories@github.com — https://github.com/traefik/traefik/releases/tag/v2.11.43
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| Go | github.com/traefik/traefik/v3 | >=3.7.0-ea.1,<3.7.0-rc.2 | 3.7.0-rc.2 |
| Go | github.com/traefik/traefik/v3 | >=3.0.0-beta1,<3.6.14 | 3.6.14 |
| Go | github.com/traefik/traefik/v2 | <2.11.43 | 2.11.43 |
| Go | github.com/traefik/traefik | <=1.7.34 | |
| GO | github.com/traefik/traefik | <= 1.7.34 | |
| GO | github.com/traefik/traefik/v2 | < 2.11.43 | 2.11.43 |
| GO | github.com/traefik/traefik/v3 | >= 3.0.0-beta1, < 3.6.14 | 3.6.14 |
| GO | github.com/traefik/traefik/v3 | >= 3.7.0-ea.1, < 3.7.0-rc.2 | 3.7.0-rc.2 |
References
- https://github.com/traefik/traefik/releases/tag/v2.11.43
- https://github.com/traefik/traefik/releases/tag/v3.6.14
- https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2
- https://github.com/traefik/traefik/security/advisories/GHSA-5m6w-wvh7-57vm
- https://nvd.nist.gov/vuln/detail/CVE-2026-39858
- https://github.com/traefik/traefik
- https://github.com/advisories/GHSA-5m6w-wvh7-57vm
CWEs
CWE-290 CWE-306
Verify integrity in audit chain (admin only). AS-IS.