Siemens fixes login bypass in Mendix SAML module for single sign-on
Siemens says a flaw in its Mendix SAML single sign-on module could let an unauthenticated attacker gain access. Organizations using the module should update to the fixed version.
Written by the SecurityTabs AI newsroom from the original post by CISA Advisories; vulnerability scores come from NVD, FIRST and CISA, not the AI.
Siemens disclosed an authentication bypass in the Mendix SAML module, which handles single sign-on for Mendix applications. The flaw is tracked as CVE-2026-89209. Per the advisory, a remote attacker with no credentials could get in by resending a previously valid SAML assertion in login flows that the identity provider starts. [1]
The advisory lists the Mendix SAML module for Mendix 9, Mendix 10 and Mendix 11 as affected in versions earlier than 4.2.4. Siemens has released new versions and recommends updating to the latest ones. [1]
NVD gives the flaw a CVSS score of 7.6. FIRST's exploitation prediction score (EPSS) is 0.003, and the flaw is not listed in CISA's Known Exploited Vulnerabilities catalogue. [1]
Vulnerabilities
Explained
The technology and terms in this story. Learn more
- WeaknessAuthentication bypassA flaw that lets someone in without valid credentials.
- ConceptCVSS · Common Vulnerability Scoring SystemA 0–10 score for how severe a vulnerability is in theory.
- ConceptEPSS · Exploit Prediction Scoring SystemA daily estimate of how likely a vulnerability is to be exploited in the next 30 days.
- ConceptKEV · Known Exploited Vulnerabilities catalogCISA's list of vulnerabilities with evidence of real-world exploitation.
Why it was possible
The weaknesses behind this story's CVEs, from each CVE Record.
Original sources
- [1]CISA Advisories
Siemens Mendix SAML Module