VulnerabilityDeferred

CVE-2026-15013

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.

CRITICAL 9.8EPSS 1.50%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (1.50%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

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.

CVSS 3.1: 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 1.50% probability · 73th percentile
CISA KEV: Not listed
Weakness: CWE-347
Source: security@wordfence.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.