SEPTEMBER 17, 2026
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Case File

CVE-2026-15981

CRITICAL · CVSS 9.8 EPSS 0.55%

Source: NVD + CISA KEV + EPSS · Published 2026-07-23 · Last synced 2026-08-22

CyberRota Analysis

AI-Generated

The SAML Single Sign On plugin for WordPress is critically vulnerable to authentication bypass, allowing unauthenticated attackers to log in as any existing user, including administrators. This is due to improper handling of the OpenSSL signature verification process, which mistakenly treats an error return value as a successful verification. WordPress site administrators using this plugin should prioritize immediate updates to mitigate the risk of unauthorized access.

CVE
CVE-2026-15981
Severity
CRITICAL
CVSS
9.8
EPSS
0.55%
WordPress OpenSSL

Original NVD Description

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.