CVE-2026-121966
Traefik before 2.11.60 and 3.7.16 ForwardAuth NTLM/Negotiate Identity Leak
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Traefik before 2.11.60 and 3.7.16 ForwardAuth NTLM/Negotiate Identity Leak
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.
- Record
CVE-2026-121966- CVSS 4.0
- 7.0 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 - 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 - Weakness
- CWE-488
- Updated
- 2026-11-04
EUVDEUVD-2026-116966
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.
- Record
EUVD-2026-116966- CVSS 4.0
- 7.0 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 - Updated
- 2026-11-04
GitHub AdvisoriesGHSA-6cm8-r9cr-2hc7
Traefik 2.x before 2.11.60 and 3.x before 3.7.16 sends ForwardAuth subrequests (and, in 3.7,...
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.
- Record
GHSA-6cm8-r9cr-2hc7- CVSS 4.0
- 7.0 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 - 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 - Weakness
- CWE-488
- Updated
- 2026-11-04
NVD
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.
- Record
CVE-2026-121966- CVSS 4.0
- 7.0 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 - 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 - Weakness
- CWE-488
- Updated
- 2026-11-04
OSV
Traefik before 2.11.60 and 3.7.16 ForwardAuth NTLM/Negotiate Identity Leak
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.
- Record
CVE-2026-121966- CVSS 4.0
- 7.0 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 - Weakness
- CWE-488
- Updated
- 2026-11-05
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, references | OSV | |
| published | EUVD, NVD | |
| published | CVE List, EUVD | |
| aliases, references | GitHub Advisories, NVD | |
| aliases, published | EUVD | |
| first indexed | CVE List |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-121966 is a high vulnerability (CVSS 7.0) in Traefik, published November 4, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.33%, the 26th percentile. No source names a fixed version.
References
github.com/traefik/traefik/security/advisories/GHSA-hrpp-p4fc-wwf8
vulncheck.com/advisories/traefik-before-2.11.60-and-3.7.16-forwardauth-ntlm-negotiate-identity-leak
nvd.nist.gov/vuln/detail/CVE-2026-121966