CVE-2026-49952 (CVSS 9.1)

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.

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CVSS v3.1 Score

9.1

CRITICAL

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

EPSS — Exploit Prediction

0.0135

Probability of exploitation

0.68%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-323 CWE-323

References

Other References

https://gitee.com/Discuz/DiscuzX/commit/9962dad52c4c6999dabaf91ecd70377c680ff3c6 https://karmainsecurity.com/KIS-2026-09 https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce https://www.vulncheck.com/advisories/discuz-x5-0-authentication-bypass-via-dbbak-php-encryption-oracle http://seclists.org/fulldisclosure/2026/Jun/3

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-49952? +

CVE-2026-49952 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0135, placing it in the 1th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-49952? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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