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NVD CRITICAL: CVE-2026-15981 — The SAML Single Sign On – SSO Login plugin for WordPress is vulnerable to Authen...

·Source: NIST NVD

Updated:

Executive Summary

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 sign

Analysis

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 WordPress user, including administrators, by submitting a crafted SAMLResponse containing an attacker-controlled NameID and a deliberately malformed signature value that triggers an OpenSSL processing error — bypassing verification entirely and resulting in wp_set_auth_cookie() being called for the targeted account. CVSS Score: 9.8. Published: 2026-07-23T21:17:03.220.

Indicators of Compromise (1)

CVE (1)
CVE-2026-15981
NVDMITRE CVE
Source Attribution

Originally published by NIST NVD on Jul 23, 2026. Verified by: NIST.

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