CVE-2026-88009 is a high severity request target routing bypass flaw in Traefik, scored 8.2. Traefik 2.11.57 and 3.7.13. Check your installed version against the affected list below, then patch or restrict access until you can. The record does not flag it as exploited.
What's affected
- Traefik before 2.11.57.
- Traefik 3.x before 3.7.13.
Severity in the record: High (8.2), vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N. Weakness: CWE-1286, CWE-444.
Fix: Traefik 2.11.57 and 3.7.13.
How to check if you're exposed
- Run
traefik version, ordocker image ls traefikfor containers. - Check whether any backend interprets an opaque request target as a path.
Run these on every host, image and build that could carry the component. Dependency files in repositories and base images in registries are easy to miss.
What to do now
- Confirm the version of every affected system using the checks above.
- Read the vendor advisory linked in Sources and note the fixed version for your release line.
- Schedule the update, starting with systems that face untrusted networks or hold the most sensitive data.
- In the meantime: after upgrading, review access logs for requests where the logged path and backend behavior differ.
- Record the change, then recheck the version to confirm it took effect.
Why it matters
Traefik accepts a rootless HTTP/1 request target that Go stores in URL.Opaque while URL.Path stays empty. Routing, path sanitization, forwardAuth, encodedCharacters checks and access logging all see a path normalized to a slash, but the opaque value is forwarded unchanged to the backend. If the backend reads that value as a path, the result can be cross-vhost routing bypass, path-scoped authorization bypass and access-log evasion. The record cites CWE-1286 and CWE-444. Its score is 8.2.
The record's KEV flag is false, so this post makes no claim that the flaw is exploited in the wild. That can change, so recheck the CISA catalog from time to time.
Libraries like this often arrive as transitive dependencies, so the version in your lockfile may not be one you chose. Safeguard's free in-browser dependency scan can show whether the package is in a project, and reachability analysis helps separate code paths that call the weak function from those that never do.
Try it yourself
Click through it at your own pace, or open it full screen.
The vector string in the record is a compact summary of how the flaw is reached and what it costs. AV is the attack vector (network, adjacent or local), PR is the privilege the attacker needs, and the C, I and A letters give the impact on confidentiality, integrity and availability. Read it against your own network layout rather than relying on the score alone.
After you patch
Patching is not the end of the job. Recheck the version on each system, because an upgrade that failed or rolled back looks the same as a success until someone looks. Keep the advisory link with your change record so the next reviewer can see why the update happened.
If you cannot patch soon, write down the reason, the compensating control you chose and a date to revisit. Exceptions without a date tend to become permanent.
Quick check
Why does access logging matter here?
The record says the logged path is normalized while the backend gets the original target, so logs can hide the request.
Sources
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Traefik: GHSA-f52w-8j3h-j724
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Safeguard Gold: CVE-2026-88009
Last reviewed: 18 October 2026.
