Traefik Labs up to 3.7.11 Kubernetes ingress-nginx provider privileges management

Summaryinfo

A vulnerability, which was classified as critical, has been found in Traefik Labs Traefik up to 3.7.11. Affected by this vulnerability is an unknown functionality of the component Kubernetes ingress-nginx provider. Performing a manipulation results in privileges management. This vulnerability is cataloged as CVE-2026-88877. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Traefik Labs Traefik up to 3.7.11. This affects an unknown functionality of the component Kubernetes ingress-nginx provider. The manipulation with an unknown input leads to a privileges management vulnerability. CWE is classifying the issue as CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Traefik is a HTTP reverse proxy and load balancer. In versions >= v3.7.0 and <= v3.7.11, the Kubernetes ingress-nginx provider mishandles Ingresses that carry both an authentication annotation and the nginx.ingress.kubernetes.io/from-to-www-redirect annotation. For such Ingresses the provider creates an additional 'sibling' router that matches on the host alone, carries only the RedirectRegex middleware, and still points at the parent router's protected backend service. Because RedirectRegex is not a terminal handler, a request its pattern does not match is forwarded to the backend, and because the redirect pattern only accepts a numeric port while Traefik's host matcher canonicalizes the authority via net.SplitHostPort, a request with a non-numeric or empty port (for example 'Host: www.example.com:x') selects the sibling router, misses the redirect, and is proxied to the protected backend with none of the Ingress's annotation-derived middlewares applied. This discards not only authentication (e.g. BasicAuth) but every annotation-derived middleware, including source-IP allowlisting. Traefik v2 and v3 releases before v3.7.0 are not affected. The issue is fixed in v3.7.12.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-88877 since 09/10/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1068 according to MITRE ATT&CK.

Upgrading to version 3.7.12 eliminates this vulnerability.

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Productinfo

Vendor

• Traefik Labs

Name

• Traefik

Version

• 3.7.0
• 3.7.1
• 3.7.2
• 3.7.3
• 3.7.4
• 3.7.5
• 3.7.6
• 3.7.7
• 3.7.8
• 3.7.9
• 3.7.10
• 3.7.11

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