Vulnerability in Cozmoslabs User Profile Builder – Beautiful Registration Forms, Profiles & Role Editor

CVE-2026-15826

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.039 (89.9th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 90th percentile — 89.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-15826: held from 0.039 to 0.039.

EPSS over last 30 days · oldest: 0.039 · newest: 0.039 · change: -0.000

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2026-15826?
CVE-2026-15826 is a critical-severity vulnerability in Cozmoslabs User Profile Builder – Beautiful Registration Forms, Profiles & Role Editor, classified under Incorrect Type Conversion or Cast. CVSS score: 9.8/10. Published 2026-08-15.
How severe is CVE-2026-15826?
Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2026-15826 known to be exploited?
1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.