Discuz! X5.0 Authentication Bypass via dbbak.php Encryption Oracle
63Vexday Risk Score
Patch soon. It has a working public exploit.
ssvc Attendcvss 9.3epss 4.2%
from disclosure to weapon2 days
Published on NVDJun 15
1st PoC+2d
exploitation probability
4.2%top 10% of all CVEs
observed exploitation
nono source reports it
4 public exploit(s)
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:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Affected products
Discuz! · Discuz! X5.0public PoCs found — 4
exploitdbwww.exploit-db.com/exploits/52621unverifiedgithubgithub.com/passwa11/CVE-2026-49952★ 3githubgithub.com/CerberusMrXi/Discuz-X5.0-Authentication-Bypass-Exploit-Framework★ 1cve_referencekarmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rceunverified⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
References
http://seclists.org/fulldisclosure/2026/Jun/3https://gitee.com/Discuz/DiscuzX/commit/9962dad52c4c6999dabaf91ecd70377c680ff3c6https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rcehttps://karmainsecurity.com/KIS-2026-09https://www.vulncheck.com/advisories/discuz-x5-0-authentication-bypass-via-dbbak-php-encryption-oracle