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.
| Vendor | Product | Versions |
|---|---|---|
| discuz! | discuz! x5.0 | 20260320, 20260501 |
Updated severity to HIGH, added affected version 20260501, and noted that the vulnerability is actively exploited with a patch available in version 20260510+.
Updated description with new details about nonce reuse and added CVE ID 2026-49952.
Initial creation
