CVE-2026-49952: Discuz! X5.0 Authentication Bypass via dbbak.php Encryption Oracle
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 loggingctl::loggingmore(), 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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Discuz! X5.0to a version that resolves this vulnerability.Fixed in 20260320 through 20260501 - Compensating control
To reduce exposure to the authentication bypass in dbbak.php (encryption oracle via the username parameter), restrict network access to the affected Discuz! instance (and specifically dbbak.php) so unauthenticated remote attackers cannot reach it.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-49952?
CVE-2026-49952 has a critical severity rating of 9.1.
How do I fix CVE-2026-49952?
To fix CVE-2026-49952, update to a patched version of Discuz! X5.0 released after May 2026.
What type of vulnerability is CVE-2026-49952?
CVE-2026-49952 is classified as an authentication bypass vulnerability.
Can CVE-2026-49952 be exploited remotely?
Yes, CVE-2026-49952 can be exploited by unauthenticated remote attackers.
What impact does CVE-2026-49952 have on security?
CVE-2026-49952 allows unauthorized access to critical database backup functionality.