CVE-2026-49952
Discuz! X5.0 Authentication Bypass via dbbak.php Encryption Oracle
- Published
- Jun 15, 2026
- Updated
- Jul 28, 2026
- Assigning CNA
- VulnCheck
- Evidence observed
- Jul 7, 2026
Primary CVSS
nvd · CVSS 4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XLow · next 30 days
- Percentile
- 91.4%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
3- CVE-2026-49952Exploit
Chaining Security Bugs in Discuz! X5.0: from Race Condition to Pre-Auth RCE
Discuz! X5.0 Authentication Bypass Exploit Framework (CVE-2026-49952) - Critical vulnerability allowing unauthenticated database backup access via UC_KEY encryption oracle token reuse. CVSS 9.1. Full-featured tool with version detection, multi-payload attacks, interactive shell, and automated exploitation. Authorized testing only.
Responsible use
Use vulnerability information only on systems you own or are authorized to test. Kitploit links to public research metadata and does not store exploit code or malicious payloads.