GHSA-46wh-3698-f2cx

Summary

There is a potential vulnerability in Traefik due to its dependency on an affected version of gRPC-Go (CVE-2026-33186).

A remote, unauthenticated attacker can send gRPC requests with a malformed HTTP/2 :path pseudo-header omitting the mandatory leading slash (e.g., Service/Method instead of /Service/Method). While the server routes such requests correctly, path-based authorization interceptors evaluate the raw non-canonical path and fail to match "deny" rules, allowing the request to bypass the policy entirely if a fallback "allow" rule is present.

Patches

• https://github.com/traefik/traefik/releases/tag/v2.11.42
• https://github.com/traefik/traefik/releases/tag/v3.6.12
• https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3

For more information

If there are any questions or comments about this advisory, please open an issue.

<details>

<summary>Original Description</summary>

Summary

This CVE hits traefik until Version 3.6.11 and 2.11.41.

gRPC-Go has an authorization bypass via missing leading slash in :path

Details

As described in https://github.com/advisories/GHSA-p77j-4mvh-x3m3

PoC

Update library version in 

https://github.com/traefik/traefik/blob/67c64ed9b25fbb90f1086977a62827133a7aa01b/go.mod#L108

Impact

Is described in https://github.com/advisories/GHSA-p77j-4mvh-x3m3

</details>

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