Traefik Routing rewriteRequestBuilder authorization

Summaryinfo

A vulnerability marked as critical has been reported in Traefik. This vulnerability affects the function rewriteRequestBuilder of the component Routing. The manipulation leads to authorization. This vulnerability is traded as CVE-2026-88009. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in Traefik (the affected version is unknown). It has been rated as critical. This issue affects the function rewriteRequestBuilder of the component Routing. The manipulation with an unknown input leads to a authorization vulnerability. Using CWE to declare the problem leads to CWE-639. The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.57, and 3.7.13, Traefik accepts a rootless HTTP/1 request target that Go stores in URL.Opaque while leaving URL.Path empty. The rewriteRequestBuilder path evaluates routing, path sanitization, forwardAuth, encodedCharacters, and access logging against a path normalized to / but forwards URL.Opaque verbatim to the backend, allowing cross-vhost routing bypass, path-scoped authorization bypass, and access-log evasion when the backend interprets the opaque target as a path. This issue is fixed in 2.11.57 and 3.7.13.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-88009 since 09/09/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/10/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• Traefik

Website

• Product: https://github.com/traefik/traefik/

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