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GHSA-46wh-3698-f2cx json

Traefik: Deny Rule Bypass via Unauthenticated Malicious gRPC Requests in gRPC-Go Dependency (CVE-2026-33186)

published 7mo ago modified 2mo ago also GO-2026-4897

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
—
no score, EPSS covers CVEs only
public exploits
0
none known

Summary

## 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](https://github.com/traefik/traefik/issues).

<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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Patch / fix

  • go github.com/traefik/traefik/v2 2.11.42
  • go github.com/traefik/traefik/v3 3.6.12, 3.7.0-ea.3

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Affected packages

ecosystem package affected fixed in
go github.com/traefik/traefik/v2
<2.11.42
2.11.42
go github.com/traefik/traefik/v3
>=3.0.0-beta3, <3.6.12
>=3.7.0-ea.1, <3.7.0-ea.3
3.6.12
3.7.0-ea.3
go github.com/traefik/traefik
all versions
 no fix listed

Classification

Weakness
  • CWE-1395 Dependency on Vulnerable Third-Party Component
  • CWE-285 Improper Authorization

References

Sources

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