Unsigned SAML LogoutRequest Acceptance in gosaml2

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary The ValidateEncodedLogoutRequestPOST function in gosaml2 accepts completely unsigned SAML LogoutRequest messages even when SkipSignatureValidation is set to false. When validateElementSignature returns dsig.ErrMissingSignature, the code in decodelogoutrequest.go:60-62 silently falls through to process the unverified XML element instead of rejecting it. An attacker who can reach the SP's Single Logout endpoint can forge a LogoutRequest for any user, terminating their session without possessing the IdP's signing key. Affected Version - Library: github.com/russellhaering/gosaml2 - Version: All versions up to and including the latest commit on main (as of 2026-03-16) - File: decodelogoutrequest.go, lines 58-69 Vulnerable Code When ErrMissingSignature is returned, the code resets el to the raw document root and continues. The requestSignatureValidated variable remains false, but no error is returned. The unsigned LogoutRequest is unmarshalled and passed to…

Published by the source

18 Mar 2026, 20:19 UTC

Last modified by the source

18 Mar 2026, 20:19 UTC

Source last checked

26 Oct 2026, 15:18 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pcgw-qcv5-h8ch

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# Patch Next advisory brief: GHSA-pcgw-qcv5-h8ch

Advisory: Unsigned SAML LogoutRequest Acceptance in gosaml2
IDs: GHSA-pcgw-qcv5-h8ch
Record: https://patchnext.com/advisories/ghsa-pcgw-qcv5-h8ch (revision 1, source checked 26 Oct 2026, 15:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/russellhaering/gosaml2 0.11.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/russellhaering/gosaml2: affected <= 0.10.0; fixed in 0.11.0

## Suggested inspection (read-only)
- Go github.com/russellhaering/gosaml2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/russellhaering/gosaml2.
- 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-pcgw-qcv5-h8ch (GitHub-reviewed advisory GHSA-pcgw-qcv5-h8ch lists affected ranges: Go github.com/russellhaering/gosaml2 >=0 <=0.10.0)

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