CVE-2026-119572 in Traefik
Summary
by MITRE • 10/30/2026
Traefik from 3.7.0-ea.1 before 3.7.15 contains an authentication bypass vulnerability in the Kubernetes Ingress NGINX provider that silently disables mTLS configured via the auth-tls-secret annotation. When another Ingress declares a path on the same host without matching auth-tls settings, Traefik falls back to default TLS options, letting unauthenticated attackers reach backends requiring client certificates.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified in Traefik versions ranging from 3.7.0-ea.1 up to but not including 3.7.15 represents a critical authentication bypass within the Kubernetes Ingress NGINX provider integration. This flaw specifically targets the handling of mutual Transport Layer Security, commonly referred to as mTLS, which is configured via the auth-tls-secret annotation in Traefik ingress resources. The core technical deficiency lies in how Traefik resolves TLS configuration when multiple ingress objects share a common host but possess divergent security requirements. In a typical Kubernetes environment, administrators may configure one ingress resource with strict client certificate validation using specific annotations while another ingress on the same hostname operates without such restrictions to serve public or less sensitive content.
When an unauthenticated request arrives for a path associated with the secure ingress that requires mTLS, Traefik incorrectly evaluates the TLS options by falling back to default settings if it encounters any other ingress declaring a path on the same host that lacks matching auth-tls configurations. This logic error results in the silent disabling of client certificate verification for requests intended for protected services. Consequently, the server accepts connections without requiring or validating the mandatory client certificates, effectively stripping away the authentication layer designed to protect backend applications from unauthorized access.
The operational impact of this vulnerability is severe, as it allows unauthenticated attackers to reach backends that are explicitly configured to require mutual TLS authentication. This bypass undermines the principle of least privilege and can lead to significant data exposure or system compromise depending on the sensitivity of the protected services. Attackers who exploit this flaw can interact with APIs, web applications, or internal microservices as if they were authenticated clients, potentially gaining access to restricted resources, sensitive user data, or administrative functions that rely on client certificate identity for authorization decisions.
From a classification perspective, this vulnerability aligns with CWE-287, which denotes Improper Authentication, specifically involving the failure to verify credentials in an authentication mechanism. It also relates to CWE-319, Cleartext Transmission of Sensitive Information, as the mTLS handshake is bypassed, potentially exposing data that should be protected by mutual identity verification. In terms of adversary behavior, this flaw facilitates initial access and privilege escalation within a Kubernetes cluster environment, mapping closely to ATT&CK techniques related to credential manipulation or abuse of trust relationships in distributed systems.
To mitigate this risk, organizations running affected versions must upgrade Traefik to version 3.7.15 or later immediately upon availability. Until the update is applied, administrators should implement network-level controls such as Kubernetes NetworkPolicies to restrict direct access to ingress controllers from untrusted sources. Additionally, reviewing and consolidating ingress configurations on shared hosts can reduce the attack surface; ensuring that all ingresses sharing a hostname enforce consistent security policies or separating them into distinct hostnames with dedicated TLS options can prevent the fallback logic from being triggered inadvertently. Regular auditing of Traefik configuration files for conflicting annotations is also recommended to maintain strict adherence to intended security postures.