CVE-2026-15013 — SAML Single Sign On <= 5.4.3 - Unauthenticated Authentication Bypass via 'SAMLResponse' Parameter Signature Algorithm Confusion
The SAML Single Sign On – SSO Login plugin for WordPress is vulnerable to Authentication Bypass via SAML Signature Algorithm Confusion in all versions up to, and including, 5.4.…
Published: 2026-07-16 · CVSS: 9.8 · CVSS 3.1
The SAML Single Sign On – SSO Login plugin for WordPress is vulnerable to Authentication Bypass via SAML Signature Algorithm Confusion in all versions up to, and including, 5.4.3. The vulnerability exists because `Mo_SAML_Utilities::mo_saml_cast_key()` reads the `SignatureMethod` Algorithm attribute directly from the attacker-controlled `SAMLResponse` parameter rather than enforcing the locally configured algorithm, causing the plugin to recast the IdP's RSA public key as an HMAC-SHA1 shared secret and validate the forged signature against it. This makes it possible for unauthenticated attackers to forge a SAML assertion targeting any WordPress account — including administrators — obtain valid WordPress authentication cookies, and achieve full administrator-level account takeover.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7