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Low, CVSS 2.1amended

Traefik: BasicAuth singleflight key collision allows authenticated identity spoofing

CVE-2026-71326GHSA-6765-c87h-8mrf

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
    >= 3.6.11, <= 3.6.24>= 3.7.0, <= 3.7.9
    Fixed in
    3.7.10, 3.6.25

  • Go github.com/traefik/traefik/v2

    Affected
    every version
    Fixed in
    no fixed version recorded

  • Go github.com/traefik/traefik

    Affected
    every version
    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
2.1 · CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-71326: 0.34% estimated exploitation activity in the next 30 days; percentile 27.11 (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 low severity vulnerability in Traefik's BasicAuth middleware. Concurrent password verifications are deduplicated through a singleflight group whose key was the delimiter-free concatenation of the submitted password and the stored secret, so a request carrying an unconfigured username — whose secret is empty — can produce the same key as a configured user's valid request and receive that request's successful result. Exploitation requires the attacker to already hold a valid credential and to read the stored password hash, which is only reachable through paths that are themselves privileged: the API is documented as admin-only, the Kubernetes path requires read access to the Secret, and the Docker path requires access to the socket. The key now encodes the password length as a prefix, so distinct (password, secret) pairs can no longer collide. Only the v3.6 line from v3.6.11 onwards and the v3.7 line are affected; earlier v3 releases and the v2 line do not carry the…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-6765-c87h-8mrf

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GO-2026-6204

  4. Revision 1 · created ·

    Published from osv record GHSA-6765-c87h-8mrf

Agent brief

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# Patch Next advisory brief: CVE-2026-71326

Advisory: Traefik: BasicAuth singleflight key collision allows authenticated identity spoofing
IDs: CVE-2026-71326, GHSA-6765-c87h-8mrf
Record: https://patchnext.com/advisories/cve-2026-71326 (revision 4, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.1)
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 3.7.10, 3.6.25. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/traefik/traefik/v3: affected >= 3.6.11, <= 3.6.24; >= 3.7.0, <= 3.7.9; fixed in 3.7.10, 3.6.25
- Go github.com/traefik/traefik/v2: affected every version
- Go github.com/traefik/traefik: affected every version

## 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://osv.dev/vulnerability/GHSA-6765-c87h-8mrf (OSV record GHSA-6765-c87h-8mrf lists affected ranges: Go github.com/traefik/traefik/v3 >=3.6.11 =3.7.0 <3.7.10 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6204 (OSV record GO-2026-6204 lists affected ranges: Go github.com/traefik/traefik >=0; Go github.com/traefik/traefik/v2 >=0; Go github.com/traefik/traefik/v3 >=3.6.11 =3.7.0 <3.7.10 (fixed))
- Verified: https://github.com/advisories/GHSA-6765-c87h-8mrf (GitHub-reviewed advisory GHSA-6765-c87h-8mrf lists affected ranges: Go github.com/traefik/traefik/v3 >=3.6.11 =3.7.0 <=3.7.9)

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