Admidio Sends SAML Response to Unvalidated Assertion Consumer Service URL from AuthnRequest

Exploitation

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

CVSS

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

EPSS

• CVE-2026-41670: 0.28% estimated exploitation activity in the next 30 days; percentile 20.54 (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.

Summary The SAML IdP implementation in Admidio's SSO module uses the AssertionConsumerServiceURL value directly from incoming SAML AuthnRequest messages as the destination for the SAML response, without validating it against the registered ACS URL (smcacsurl) stored in the database for the corresponding service provider client. An attacker who knows the Entity ID of a registered SP client can craft a SAML AuthnRequest with an arbitrary AssertionConsumerServiceURL, causing the IdP to send the signed SAML response -- containing user identity attributes (login name, email, roles, profile fields) -- to an attacker-controlled URL. Details The vulnerability is in src/SSO/Service/SAMLService.php, in handleSSORequest() at lines 439-465: There is no code that compares $clientACS against the client's registered smcacsurl column value. The SAML 2.0 specification and OASIS security considerations explicitly require IdPs to verify that the AssertionConsumerServiceURL matches one of the SP's…

Published by the source

29 Apr 2026, 21:57 UTC

Last modified by the source

8 May 2026, 20:14 UTC

Source last checked

26 Oct 2026, 14:40 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-p9w9-87c8-m235

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

# Patch Next advisory brief: CVE-2026-41670

Advisory: Admidio Sends SAML Response to Unvalidated Assertion Consumer Service URL from AuthnRequest
IDs: CVE-2026-41670, GHSA-p9w9-87c8-m235
Record: https://patchnext.com/advisories/cve-2026-41670 (revision 1, source checked 26 Oct 2026, 14:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: admidio/admidio 5.0.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist admidio/admidio: affected <= 5.0.8; fixed in 5.0.9

## Suggested inspection (read-only)
- Packagist admidio/admidio: 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 admidio/admidio.
- 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-p9w9-87c8-m235 (GitHub-reviewed advisory GHSA-p9w9-87c8-m235 lists affected ranges: Packagist admidio/admidio >=0 <=5.0.8)

Commands are suggestions: review each one before running it.