CVE-2026-15826

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

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.

We have discovered 10,704 live websites that are affected by CVE-2026-15826.

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Affected Software

Product  Profile Builder
Category Wordpress Plugins
Vulnerable Domains10,704 live websites (88% of Profile Builder install base)
Vulnerable Versions
  • from 0 through 3.16.4
Vulnerable Versions Count208 versions ( 99% of all versions)


Common Weakness Enumeration

CWE-704 Incorrect Type Conversion or Cast



Details

  • Published - Aug 15, 2026
  • Updated - Aug 17, 2026

Credits

  • Supakiad S. (m3ez) (finder)

Website Distribution by Country

Number of websites using CVE-2026-15826
United States3,692 websites


Italy813 websites
Germany743 websites
GB547 websites
France529 websites
Netherlands483 websites
Spain342 websites
Russia275 websites
Canada250 websites
Australia209 websites

Website Distribution by TLD

Number of websites using CVE-2026-15826
.com4,203 websites
.org1,034 websites
.it576 websites
.nl442 websites
.de356 websites
.co.uk271 websites
.net237 websites
.ru223 websites
.fr200 websites
.com.au167 websites

Vulnerable Versions

Vulnerable versions are highlighted in red

Websites affected by CVE-2026-15826

Top websites that are affected by CVE-2026-15826. Please click on the "Contact us" link to get more information.
DomainCountryRankContacts
*****.com United States*,***
******.com United States**,***
*****.com United States**,***
*******.it Italy**,***
***********.com United States**,***
********.dk Denmark**,***
*******.com United States**,***
********.com United States**,***
************.com United States**,***
******.ru Russia**,***
See full domain list

FAQ

CVE-2026-15826 is Incorrect Type Conversion or Cast in Profile Builder
A total of 10,704 websites have been identified as vulnerable to CVE-2026-15826, based on global website indexing conducted by WebTechSurvey.
The Profile Builder is affected by the CVE-2026-15826 vulnerability.
Profile Builder versions up to and including 3.16.4 are vulnerable to CVE-2026-15826.

References