Vulnerability in Discuz! X5.0
CVE-2026-49952
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.
EPSS: 0.047 (91.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
Affected products
- Discuz! X5.0 — versions 20260320
Weakness classification (CWE)
Public proof-of-concept exploits
References
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (exploit)
- disclosure@vulncheck.com (patch)
- disclosure@vulncheck.com (third-party-advisory)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2026-49952?
- CVE-2026-49952 is a critical-severity vulnerability in Discuz! X5.0, classified under Reusing a Nonce, Key Pair in Encryption. CVSS score: 9.1/10. Published 2026-06-15.
- How severe is CVE-2026-49952?
- Critical severity. CVSS v3 base score is 9.1 out of 10.
- Is CVE-2026-49952 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.