CVE-2026-15981 SAML Single Sign On <= 5.4.4 - Unauthenticated Authentication Bypass via SAMLResponse Parameter
Unauthenticated attackers can bypass SAML signature verification to log in as any user, including administrators, due to a flawed boolean check.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-15981?
CVE-2026-15981 is a critical authentication bypass vulnerability in cyberlord92 SAML Single Sign On – SSO Login, published on 23 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-287
Which versions are affected by CVE-2026-15981?
How do I fix CVE-2026-15981?
No fix has been published for CVE-2026-15981 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-15981 being exploited?
There is no known exploitation of CVE-2026-15981 in the wild and no public exploit code.
Public exploit code: 2 proofs of concept on GitHub.
Sources
Also known as GHSA-wgjx-q85h-87v2.