CVE-2026-15826: User Profile Builder <= 3.16.4 - Unauthenticated Authentication Bypass via Type Confusion to Administrator Account Takeover via 'username' Parameter

1. In CISA KEV: not seen
2. Exploited (reported): not seen
3. Scanning observed: not seen
4. Proof of concept public1 public GitHub repository (unverified), listed by PoC-in-GitHub17 Aug
5. Not established: not seen

DescriptionNVD

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.

Exploitation

Check available, not yet exploited. A public nuclei template can confirm it on a system you are authorised to test.

CISA KEV

Not listed

Public check

User Profile Builder 3.16.4 - Unauthenticated Authentication Bypass · nuclei template in projectdiscovery/nuclei-templates

Weakness

Incorrect Type Conversion or Cast · Memory Corruption

Vendor

cozmoslabs

Published

August 2026

Band

Check available, not yet exploited, August 2026

1. 17 Aug
   PoC-in-GitHub lists 1 public GitHub repository (unverified) PoC-in-GitHub

• NVD entrynvd.nist.gov
• Vendor advisorywordfence.com
• CVE recordcve.org
• Weakness CWE-704cwe.mitre.org