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.

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.

Published 2026-06-15 · last modified 2026-10-25.

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.

EPSS exploit prediction

EPSS: 0.047 (91.8th percentile), scored 2026-11-01.

Low probability of exploitation in the next 30 days, but still tracked. 92nd percentile — 91.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.037 · newest: 0.047 · change: +0.011

Affected products

Discuz! X5.0 — versions 20260320

Weakness classification (CWE)

CWE-323 — Reusing a Nonce, Key Pair in Encryption

Public proof-of-concept exploits

References

karmainsecurity.com/KIS-2026-09 (technical-description)
karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce (exploit)
gitee.com/Discuz/DiscuzX/commit/9962dad52c4c6999dabaf91ecd70377c680ff3c6 (patch)
www.vulncheck.com/advisories/discuz-x5-0-authentication-bypass-via-dbbak-php-en… (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.