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.

CVSS v4.0

9.3 CRITICALCVSS: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:X

CVSS v3.1

9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

4.72% chance of exploitation in the next 30 days, 91th percentile

Nuclei

critical · CWE-323

Published

2026-06-15

Updated

2026-07-28

Proof-of-concept exploits (2)

• https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce
• passwa11/CVE-2026-499523★ · 2026-06-17

Nuclei templates (1)

• projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-49952.yaml

ExploitDB entries (1)

• https://www.exploit-db.com/exploits/52621

References

• CVE Record
• NVD entry

Related

• CVE-2023-20562
• CVE-2023-29017
• CVE-2023-3519
• CVE-2023-38646
• CVE-2023-4357
• CVE-2023-47218