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CVE-2026-15013

CRITICALCVSS 9.8/10EPSS 0.44%

Last modified

CVE-2026-15013 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 0.44% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
9.8/10

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

EPSS Probability
0.44%

36.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
cyberlord92SAML Single Sign On – SSO Login<= 5.4.3

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is 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. 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.
How severe is CVE-2026-15013?
CVE-2026-15013 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.44% probability of exploitation in the next 30 days.
How do I fix CVE-2026-15013?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST