CVSS v3
9.8
CRITICAL
EPSS Score
0.5%
exploit probability
CISA KEV
No
known exploited
Exploitation
—
SSVC status
The SAML Single Sign On – SSO Login plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 5.4.4. This is due to the mo_saml_validate_signature() function performing a loose boolean check on the raw tri-state integer returned by PHP's openssl_verify(), causing an error return value of -1 to be evaluated as truthy and therefore treated as a successful signature verification. This makes it possible for unauthenticated attackers to log in as any existing W
The SAML Single Sign On – SSO Login plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 5.4.4. This is due to the mo_saml_validate_signature() function performing a loose boolean check on the raw tri-state integer returned by PHP's openssl_verify(), causing an error return value of -1 to be evaluated as truthy and therefore treated as a successful signature verification. This makes it possible for unauthenticated attackers to log in as any existing W
Active exploitation of CVE-2026-15981 has not been confirmed. The EPSS score is 0.5%, indicating the estimated probability of exploitation in the next 30 days.
CVE-2026-15981 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string 3.1.
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