Insufficient verification of data authenticity in SimpleSAMLphp - CVE-2026-49284
Published: May 31, 2026
Vulnerability identifier: #VU133100
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-49284
CWE-ID: CWE-345
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: SimpleSAMLphp
Affected software:
SimpleSAMLphp
SimpleSAMLphp
Detailed vulnerability description
The vulnerability allows a remote user to bypass authentication and authorization checks.
The vulnerability exists due to insufficient verification of data authenticity in the SAML SP ACS path when processing a valid response from an unexpected trusted IdP with an unsigned Response/InResponseTo and no SubjectConfirmationData/InResponseTo in the signed assertion. A remote user can obtain a signed assertion from a lower-trust trusted IdP and submit it to satisfy SP state created for a different expected IdP to bypass authentication and authorization checks.
The issue is relevant in multi-IdP deployments where authorization decisions depend on the selected or expected IdP.
How to mitigate CVE-2026-49284
Install security update from vendor's website.