CVE-2026-49952: Discuz! x5.0

Critical severity, CVSS 9.1. EPSS: 3.7% chance of exploitation in the next 30 days.

Discuz! X5.0 releases 20260320 through 20260501 contains an authentication bypass vulnerability that allows unauthenticated remote attackers to gain unauthorized access to database backup and restore functionality by exploiting a shared cryptographic key between UCenter integration and the database backup API exposed by dbbak.php. Attackers can inject a crafted payload through the username parameter during login to abuse the encryption oracle in logging_ctl::logging_more(), obtain a legitimately signed token, and use it to bypass authorization for database export and import operations, with the additional ability to trigger a race condition to impersonate arbitrary users.

Affected products

• Discuz! Discuz! x5.0: from 20260320, up to and including 20260501

Published 2026-06-15. Last modified 2026-06-17.