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Medium, CVSS 4.8amended

Traefik: allowCrossNamespace=false bypass via @kubernetescrd TraefikService backendRef

CVE-2026-71325GHSA-62fc-8686-hfmq

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
    >= 3.0.0, <= 3.6.24>= 3.7.0, <= 3.7.9
    Fixed in
    3.7.10, 3.6.25

  • Go github.com/traefik/traefik/v2

    Affected
    <= 2.11.53
    Fixed in
    2.11.54

  • 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
4.8 · CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N · score source
EPSS
  • CVE-2026-71325: 0.15% estimated exploitation activity in the next 30 days; percentile 4.65 (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 medium severity vulnerability in Traefik's Kubernetes CRD provider. When providers.kubernetesCRD.allowCrossNamespace is disabled — the default — cross-namespace @kubernetescrd references are rejected for middlewares, TLS options and HTTP/TCP ServersTransports, but the same restriction was not applied to TraefikService backend references resolved by the service resolver. A tenant confined by RBAC to a single namespace can therefore bind its own router to a TraefikService owned by another namespace and expose or reroute that namespace's backend, defeating the namespace isolation allowCrossNamespace=false is meant to enforce. Traefik v2 releases and the unmaintained v3 minor lines below v3.6 are affected and will not receive a patch on their own line; the remedy for those users is upgrading to a maintained, patched release. Patches - https://github.com/traefik/traefik/releases/tag/v2.11.54 - https://github.com/traefik/traefik/releases/tag/v3.6.25 -…

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

    Amended from ghsa record GHSA-62fc-8686-hfmq

  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-2026-6203

  4. Revision 1 · created ·

    Published from osv record GHSA-62fc-8686-hfmq

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-71325

Advisory: Traefik: `allowCrossNamespace=false` bypass via `@kubernetescrd` TraefikService backendRef
IDs: CVE-2026-71325, GHSA-62fc-8686-hfmq
Record: https://patchnext.com/advisories/cve-2026-71325 (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: Medium (CVSS 4.8)
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 3.7.10, 3.6.25; github.com/traefik/traefik/v2 2.11.54. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/traefik/traefik/v3: affected >= 3.0.0, <= 3.6.24; >= 3.7.0, <= 3.7.9; fixed in 3.7.10, 3.6.25
- Go github.com/traefik/traefik/v2: affected <= 2.11.53; fixed in 2.11.54
- 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://osv.dev/vulnerability/GHSA-62fc-8686-hfmq (OSV record GHSA-62fc-8686-hfmq lists affected ranges: Go github.com/traefik/traefik/v2 >=0 =3.0.0 =3.7.0 =0 <=1.7.34)
- Verified: https://osv.dev/vulnerability/GO-2026-6203 (OSV record GO-2026-6203 lists affected ranges: Go github.com/traefik/traefik >=0; Go github.com/traefik/traefik/v2 >=0 =3.0.0 =3.7.0 <3.7.10 (fixed))
- Verified: https://github.com/advisories/GHSA-62fc-8686-hfmq (GitHub-reviewed advisory GHSA-62fc-8686-hfmq lists affected ranges: Go github.com/traefik/traefik/v2 >=0 =3.0.0 =3.7.0 =0 <=1.7.34)

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