# CVE-2026-121966: Traefik before 2.11.60 and 3.7.16 ForwardAuth NTLM/Negotiate Identity Leak

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

Traefik 2.x before 2.11.60 and 3.x before 3.7.16 sends ForwardAuth subrequests (and, in 3.7, Ingress NGINX auth-url requests) through an auth-server connection pool shared by all clients, exposing connection-bound NTLM or Negotiate authentication. An unauthenticated attacker can reuse another user's authenticated connection, receiving the victim's identity via authResponseHeaders to access backends as that user.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- traefik / traefik (github.com/traefik/traefik/v2): ≥ 0; < 2.11.60 (affected, semver); 2.11.60 (unaffected, semver). Source: CNA: VulnCheck
- traefik / traefik (github.com/traefik/traefik/v3): ≥ 3.0.0; < 3.7.16 (affected, semver); 3.7.16 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 7 (high); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 8.7 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N; source: CNA: VulnCheck

- CVSS 4.0: 7 (high); CVSS:4.0/AV:N/AC:L/AT:P/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 8.7 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-488

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/traefik/traefik/security/advisories/GHSA-hrpp-p4fc-wwf8 (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/traefik-before-2.11.60-and-3.7.16-forwardauth-ntlm-negotiate-identity-leak (CNA: VulnCheck; third-party-advisory)

- https://github.com/traefik/traefik/security/advisories/GHSA-hrpp-p4fc-wwf8 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/traefik-before-2.11.60-and-3.7.16-forwardauth-ntlm-negotiate-identity-leak (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121966; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121966; retrieved 2026-11-04; source updated 2026-11-04

Revision: 0c805d81038240cde71603c7c94899810ecb6ff191499c7a9ae24c62e5cfff21

Canonical: https://y2.dev/cve/CVE-2026-121966

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