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Description

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.

PUBLISHED Reserved 2026-06-02 | Published 2026-06-15 | Updated 2026-06-16 | Assigner VulnCheck




CRITICAL: 9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

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

Problem types

Reusing a Nonce, Key Pair in Encryption

Product status

Default status
affected

20260320 (date)
affected

Credits

Egidio Romano finder

References

seclists.org/fulldisclosure/2026/Jun/3

karmainsecurity.com/KIS-2026-09 technical-description

karmainsecurity.com/...-in-discuz-from-race-condition-to-rce exploit

gitee.com/...commit/9962dad52c4c6999dabaf91ecd70377c680ff3c6 patch

www.vulncheck.com/...-bypass-via-dbbak-php-encryption-oracle third-party-advisory

cve.org (CVE-2026-49952)

nvd.nist.gov (CVE-2026-49952)

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