Executive brief
Mendix SAML, an authentication module used to enable single sign-on (SSO) in Mendix applications, contains a flaw in its signature verification logic. An unauthenticated attacker can exploit this to forge or bypass SAML authentication responses in certain SSO configurations, allowing them to hijack user accounts and gain unauthorized access to applications without valid credentials.
Technical details
The Mendix SAML module fails to properly validate the cryptographic signature on SAML authentication responses, a violation of the SAML specification (CWE-347). An unauthenticated remote attacker can craft a malicious SAML response with invalid or absent signatures that the module will accept, leading to arbitrary account hijacking in specific SSO deployments. The vulnerability requires specific SSO configuration and user interaction but no prior authentication. Patches are available: update Mendix SAML (Mendix 9.24 compatible) to v3.6.27+, Mendix SAML (Mendix 10 compatible) to v4.2.3+, or Mendix SAML (Mendix 11 compatible) to v4.2.3+.
Affected products
- Siemens Mendix SAML (Mendix 9.24 compatible) All versions < 3.6.27
- Siemens Mendix SAML (Mendix 10 compatible) All versions < 4.2.3
- Siemens Mendix SAML (Mendix 11 compatible) All versions < 4.2.3
Timeline
- 2026-09-03: disclosed