CVE-2026-15981

Name of the Vulnerable Software and Affected Versions SAML Single Sign On – SSO Login versions prior to 5.4.5

Description An authentication bypass exists due to the mo saml validate signature() function performing a loose boolean check on the integer returned by PHP's openssl verify(). An error return value of -1 is evaluated as true, which is treated as a successful signature verification. Unauthenticated attackers can log in as any WordPress user, including administrators, by submitting a crafted SAMLResponse with an attacker-controlled NameID and a malformed signature value that triggers an OpenSSL processing error, leading to the execution of wp set auth cookie() for the targeted account.

Recommendations Update the plugin to a version newer than 5.4.4.