Header dropping in traefik

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.8 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS

• CVE-2021-32813: 1.10% estimated exploitation activity in the next 30 days; percentile 65.71 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact There exists a potential header vulnerability in Traefik's handling of the Connection header. Active exploitation of this issue is unlikely, as it requires that a removed header would lead to a privilege escalation, however, the Traefik team has addressed this issue to prevent any potential abuse. Details If you have a chain of Traefik middlewares, and one of them sets a request header Important-Security-Header, then sending a request with the following Connection header will cause it to be removed before the request was sent: In this case, the backend does not see the request header Important-Security-Header. Patches Traefik v2.4.x: https://github.com/traefik/traefik/releases/tag/v2.4.13 Workarounds No. For more information If you have any questions or comments about this advisory, open an issue.

Published by the source

5 Aug 2021, 17:04 UTC

Last modified by the source

1 Feb 2023, 05:06 UTC

Source last checked

26 Oct 2026, 14:54 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-m697-4v8f-55qg

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# Patch Next advisory brief: CVE-2021-32813

Advisory: Header dropping in traefik
IDs: CVE-2021-32813, GHSA-m697-4v8f-55qg
Record: https://patchnext.com/advisories/cve-2021-32813 (revision 1, source checked 26 Oct 2026, 14:54 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/v2 2.4.13. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/traefik/traefik/v2: affected < 2.4.13; fixed in 2.4.13
- Go github.com/traefik/traefik: affected <= 1.7.30

## Suggested inspection (read-only)
- 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/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-m697-4v8f-55qg (GitHub-reviewed advisory GHSA-m697-4v8f-55qg lists affected ranges: Go github.com/traefik/traefik/v2 >=0 =0 <=1.7.30)

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