CVE-2026-15981 | defend.network

What is 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. 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.

CVSS9.8 NVD 3.1

SeverityCRITICAL

ExploitationNo exploitation reported

EPSS1% · P54

Triage statusNo Known Exploit

ActionPatch within 48 hours

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

NVD published2026-07-23

NVD last modified2026-07-24

Timeline

2026-07-23Published to the U.S. National Vulnerability Database (NVD)
2026-07-24NVD record last updated
2026-08-26First covered in a defend.network daily briefing

Affected product

See advisory

Remediation Steps

Apply the vendor security update for MiniOrange SAML 2.0 SSO Plugin (WordPress) as a priority.
Restrict network exposure of the affected service to trusted sources until patched.
Review logs and detections for indicators of exploitation.
Confirm fixed versions against the official vendor advisory before deploying.

References

Referenced in our briefings & reports

Vulnerability Priority Report – Week 4 of August 2026 (August 24 – 30)
Mirage2FA hits 4,500 orgs; Oracle Weblogic RCE, NVIDIA AI poisoning, WordPress plugin flaws (2026-08-26)

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🤖 This CVE page is generated by defend.network from NVD, CISA KEV, EPSS, and our verified daily briefings. Severity and exploitation data come from official sources; always verify remediation steps against the official vendor advisory before acting in production.