Traefik up to 2.11.42/3.6.13/3.7.0-rc.1 Reverse Proxy spec.chain.middlewares middlewares[] authorization

Summaryinfo

A vulnerability was found in Traefik up to 2.11.42/3.6.13/3.7.0-rc.1. It has been declared as problematic. This impacts the function spec.chain.middlewares of the component Reverse Proxy Handler. Such manipulation of the argument middlewares[] leads to authorization. This vulnerability is referenced as CVE-2026-41174. The attack can only be performed from a local environment. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Traefik up to 2.11.42/3.6.13/3.7.0-rc.1. Affected by this issue is the function spec.chain.middlewares of the component Reverse Proxy Handler. The manipulation of the argument middlewares[] with an unknown input leads to a authorization vulnerability. Using CWE to declare the problem leads to CWE-863. The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a potential vulnerability in Traefik's Kubernetes CRD provider cross-namespace isolation enforcement. When providers.kubernetesCRD.allowCrossNamespace=false, Traefik correctly rejects direct cross-namespace middleware references from IngressRoute objects, but fails to apply the same restriction to middleware references nested inside a Chain middleware's spec.chain.middlewares[]. An actor with permission to create or update Traefik CRDs in their own namespace can exploit this to cause Traefik to resolve and apply middleware objects from another namespace, bypassing the documented isolation boundary. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-41174 since 04/17/2026. The exploitation is known to be easy. The attack needs to be approached locally. There are known technical details, but no exploit is available.

Upgrading to version 2.11.43, 3.6.14 or 3.7.0-rc.2 eliminates this vulnerability.

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Productinfo

Name

• Traefik

Version

• 2.11.0
• 2.11.1
• 2.11.2
• 2.11.3
• 2.11.4
• 2.11.5
• 2.11.6
• 2.11.7
• 2.11.8
• 2.11.9
• 2.11.10
• 2.11.11
• 2.11.12
• 2.11.13
• 2.11.14
• 2.11.15
• 2.11.16
• 2.11.17
• 2.11.18
• 2.11.19
• 2.11.20
• 2.11.21
• 2.11.22
• 2.11.23
• 2.11.24
• 2.11.25
• 2.11.26
• 2.11.27
• 2.11.28
• 2.11.29
• 2.11.30
• 2.11.31
• 2.11.32
• 2.11.33
• 2.11.34
• 2.11.35
• 2.11.36
• 2.11.37
• 2.11.38
• 2.11.39
• 2.11.40
• 2.11.41
• 2.11.42
• 3.6.0
• 3.6.1
• 3.6.2
• 3.6.3
• 3.6.4
• 3.6.5
• 3.6.6
• 3.6.7
• 3.6.8
• 3.6.9
• 3.6.10
• 3.6.11
• 3.6.12
• 3.6.13
• 3.7.0-rc.0
• 3.7.0-rc.1

Website

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

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