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High, CVSS 7.8

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

GHSA-46wh-3698-f2cx

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/traefik/traefik/v3 3.7.0-ea.3, 3.6.12; github.com/traefik/traefik/v2 2.11.42), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
7.8 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

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 <summaryOriginal Description</summary Summary This CVE hits traefik until Version 3.6.11 and 2.11.41. gRPC-Go has an authorization…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-46wh-3698-f2cx

Agent brief

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# Patch Next advisory brief: GHSA-46wh-3698-f2cx

Advisory: Traefik: Deny Rule Bypass via Unauthenticated Malicious gRPC Requests in gRPC-Go Dependency (CVE-2026-33186)
IDs: GHSA-46wh-3698-f2cx
Record: https://patchnext.com/advisories/ghsa-46wh-3698-f2cx (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/traefik/traefik/v3 3.7.0-ea.3, 3.6.12; github.com/traefik/traefik/v2 2.11.42. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/traefik/traefik/v3: affected >= 3.0.0-beta3, < 3.6.12; >= 3.7.0-ea.1, < 3.7.0-ea.3; fixed in 3.6.12, 3.7.0-ea.3
- Go github.com/traefik/traefik/v2: affected < 2.11.42; fixed in 2.11.42

## Suggested inspection (read-only)
- Go github.com/traefik/traefik/v3: check the installed version with your package manager.
- Go github.com/traefik/traefik/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/traefik/traefik/v3, github.com/traefik/traefik/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-46wh-3698-f2cx (GitHub-reviewed advisory GHSA-46wh-3698-f2cx lists affected ranges: Go github.com/traefik/traefik/v2 >=0 =3.0.0-beta3 =3.7.0-ea.1 <3.7.0-ea.3)

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