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CVE-2026-15826

9.8 · CRITICAL

The User Profile Builder plugin for WordPress is vulnerable to Authentication Bypass via Type Confusion in versions up to, and including, 3.16.4.

Published Aug 15, 2026CWE-704EPSS 3.90%

Overview

CVE-2026-15826 is a critical-severity vulnerability. It was published on August 15, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

The User Profile Builder plugin for WordPress is vulnerable to Authentication Bypass via Type Confusion in versions up to, and including, 3.16.4. This is due to the wppb_log_in_user() function calling absint() on the return value of wp_insert_user() before performing an is_wp_error() check — when a registration is submitted with a 61–70 character username, WordPress core rejects it with a WP_Error object, but absint() coerces that object to the integer 1 before the error check can short-circuit execution, causing the plugin to bind and return a transient-backed autologin nonce tied to user ID 1. This makes it possible for unauthenticated attackers to log in as the site's Administrator account (user ID 1), resulting in full administrative takeover of the site.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refplugins.trac.wordpress.org/browser/profile-builder/tags/3.16.4/features/functions.php#L1481Refplugins.trac.wordpress.org/browser/profile-builder/tags/3.16.4/front-end/class-formbuilder.php#L262Refplugins.trac.wordpress.org/browser/profile-builder/tags/3.16.4/front-end/class-formbuilder.php#L364Refplugins.trac.wordpress.org/browser/profile-builder/tags/3.16.4/front-end/class-formbuilder.php#L742Refplugins.trac.wordpress.org/browser/profile-builder/tags/3.16.4/front-end/class-formbuilder.php#L945Refplugins.trac.wordpress.org/browser/profile-builder/tags/3.16.4/front-end/default-fields/username/username.php#L28Refplugins.trac.wordpress.org/browser/profile-builder/tags/3.16.4/front-end/default-fields/username/username.php#L49Refplugins.trac.wordpress.org/changeset/3609855/profile-builderRefwww.wordfence.com/threat-intel/vulnerabilities/id/9f606fba-f779-42ea-a160-6c3b20dc5e79?source=cve

How CyberStrike helps

Frequently asked questions

What is CVE-2026-15826?

CVE-2026-15826 is a critical-severity vulnerability. It was published on August 15, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-15826?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-15826?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-15826?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-15826 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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