VulnerabilityAwaiting Analysis

CVE-2026-15981

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.

CRITICAL 9.8EPSS 0.81%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.81%). 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 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 3.1: 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.81% probability · 55th percentile
CISA KEV: Not listed
Weakness: CWE-287
Source: security@wordfence.com

References

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