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High, CVSS 7.8

Traefik's ForwardAuth trustForwardHeader=false allows spoofed X-Forwarded-Prefix to bypass authentication

CVE-2026-35051GHSA-6384-m2mw-rf54

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

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

  • Go github.com/traefik/traefik/v3

    Affected
    >= 3.7.0-ea.1, < 3.7.0-rc.2>= 3.0.0-beta1, < 3.6.14
    Fixed in
    3.7.0-rc.2, 3.6.14

  • Go github.com/traefik/traefik/v2

    Affected
    < 2.11.43
    Fixed in
    2.11.43

  • Go github.com/traefik/traefik

    Affected
    <= 1.7.34
    Fixed in
    no fixed version recorded

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:L/SA:N · score source
EPSS
  • CVE-2026-35051: 0.27% estimated exploitation activity in the next 30 days; percentile 18.94 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary There is a high-severity authentication bypass vulnerability in Traefik's ForwardAuth middleware when trustForwardHeader=false is configured and Traefik is deployed behind a trusted upstream proxy. While X-Forwarded- headers (such as X-Forwarded-For, X-Forwarded-Host, and X-Forwarded-Proto) from trusted context are correctly rebuilt, it does not strip or rebuild X-Forwarded-Prefix, leaving any attacker-supplied value intact in the subrequest forwarded to the authentication service. When the authentication service makes authorization decisions based on X-Forwarded-Prefix, an external attacker can spoof a trusted prefix value and gain unauthorized access to protected backend routes. Patches - https://github.com/traefik/traefik/releases/tag/v2.11.43 - https://github.com/traefik/traefik/releases/tag/v3.6.14 - https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2 For more information If there are any questions or comments about this advisory, please open an issue. <details…

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

    Published from ghsa record GHSA-6384-m2mw-rf54

Agent brief

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# Patch Next advisory brief: CVE-2026-35051

Advisory: Traefik's ForwardAuth trustForwardHeader=false allows spoofed X-Forwarded-Prefix to bypass authentication
IDs: CVE-2026-35051, GHSA-6384-m2mw-rf54
Record: https://patchnext.com/advisories/cve-2026-35051 (revision 1, source checked 26 Oct 2026, 15:20 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: Partial vendor fix; fixed versions by package: github.com/traefik/traefik/v3 3.7.0-rc.2, 3.6.14; github.com/traefik/traefik/v2 2.11.43. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/traefik/traefik/v3: affected >= 3.7.0-ea.1, < 3.7.0-rc.2; >= 3.0.0-beta1, < 3.6.14; fixed in 3.7.0-rc.2, 3.6.14
- Go github.com/traefik/traefik/v2: affected < 2.11.43; fixed in 2.11.43
- Go github.com/traefik/traefik: affected <= 1.7.34

## 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.
- Go github.com/traefik/traefik: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## 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, github.com/traefik/traefik.
- 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-6384-m2mw-rf54 (GitHub-reviewed advisory GHSA-6384-m2mw-rf54 lists affected ranges: Go github.com/traefik/traefik/v3 >=3.7.0-ea.1 =3.0.0-beta1 =0 =0 <=1.7.34)

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