CVE-2026-114640 traefik CVE debrief

Who should care

Defenders responsible for Traefik instances, especially those using the Kubernetes Ingress-NGINX provider, should assess exposure and verify configurations to prevent potential authentication bypass attacks.

Why it matters

CVE-2026-114640 is an authentication bypass vulnerability in Traefik's Kubernetes Ingress-NGINX provider that allows unauthenticated attackers to impersonate mTLS identities. Defenders should verify exposure, assess configurations, and consider updating to mitigate the vulnerability.

• Verification of Traefik instance exposure and configuration is required to prevent potential authentication bypass attacks.
• Defenders need to assess the configuration of ssl-redirect and auth-tls-pass-certificate-to-upstream to determine if the vulnerability is exploitable.
• Updating to Traefik version 3.7.14 or later can mitigate the vulnerability.
• Further verification of affected versions and remediation efforts may be necessary based on the specific deployment context.

Technical summary

The vulnerability is caused by Traefik forwarding client-supplied Ssl-Client-* headers on the plaintext HTTP router when ssl-redirect is disabled alongside auth-tls-pass-certificate-to-upstream. This allows unauthenticated attackers to send Ssl-Client-Verify: SUCCESS with a chosen certificate subject and issuer to impersonate mTLS identities. The vulnerability affects Traefik versions from 3.7.0 before 3.7.14 and has been publicly disclosed. Defenders should verify exposure and assess configurations to prevent potential authentication bypass attacks.

Defensive priority

Defenders should prioritize verifying exposure of Traefik instances, especially those using the Kubernetes Ingress-NGINX provider, and assess the configuration of ssl-redirect and auth-tls-pass-certificate-to-upstream.

Recommended defensive actions

• Verify Traefik instance exposure and configuration
• Assess ssl-redirect and auth-tls-pass-certificate-to-upstream settings
• Update to Traefik version 3.7.14 or later
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description, CVSS score, and affected versions. Vendor advisories are available for further information. The vulnerability has been publicly disclosed and defenders should verify exposure and assess configurations to prevent potential authentication bypass attacks. The Traefik project has released a patch for the vulnerability, which is available in version 3.7.14 or later.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.