# Siemens Mendix SAML module auth bypass patched

Published: 2026-10-29 · Severity: routine · Sectors: Manufacturing, Technology
Canonical: https://vorant.io/reports/fff4de90-599b-55f6-b7c3-5b3720431862/siemens-mendix-saml-module-auth-bypass-patched
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> Siemens patched an authentication bypass in the Mendix SAML module that lets attackers replay valid SAML assertions to gain unauthorized access.

Source: cisa.gov — https://www.cisa.gov/news-events/ics-advisories/icsa-26-302-01

## What to check

- Applies to: The 1 CVE named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation: No exploitation in the wild and no public exploit is recorded for the CVEs named.

Siemens disclosed an authentication bypass vulnerability (CVE-2026-89209) in the Mendix SAML module affecting Mendix 9, 10, and 11 compatible versions. The flaw allows an unauthenticated remote attacker to gain unauthorized access by replaying a valid SAML assertion in IdP-initiated authentication flows, classified as Authentication Bypass by Capture-replay (CWE-294). The CVSS v3 score is 6.8, reflecting a moderate severity issue that nonetheless undermines a core authentication control.

Affected products include Mendix SAML (Mendix 10 compatible) versions prior to 4.2.4, Mendix SAML (Mendix 11 compatible) versions prior to 4.2.4, and Mendix SAML (Mendix 9 compatible) versions prior to 3.6.29. Siemens has released updated versions addressing the vulnerability and recommends all users update immediately. The vulnerability was reported to CISA by Siemens ProductCERT, and there is no indication in this advisory of active exploitation in the wild.

This advisory affects organizations in Critical Manufacturing and Information Technology sectors worldwide using Mendix low-code applications with SAML-based SSO via IdP-initiated flows. CISA recommends standard ICS defensive measures in addition to patching: minimizing network exposure of control system devices, isolating control networks behind firewalls, and using secure remote access methods such as updated VPNs. Defenders should prioritize upgrading the Mendix SAML module to the fixed versions and review SAML assertion handling/logging for signs of replay attempts.

## Mentioned in this report

- Vulnerabilities: CVE-2026-89209

Source reporting: https://www.cisa.gov/news-events/ics-advisories/icsa-26-302-01

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