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CWE-323Weakness · CWE-323

CVE-2026-49952

CRITICAL · 9.1 CVSS v3.1 Published 2026-06-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Discuz! X5.0 versions 20260320-20260501 contain an authentication bypass vulnerability in dbbak.php where a shared cryptographic key between UCenter and the database backup API allows attackers to obtain legitimate signed tokens. By injecting a crafted payload through the username parameter during login, attackers abuse an encryption oracle in logging_ctl::logging_more() to bypass authorization for database export/import operations and impersonate users via a race condition.

MitigationDisable the encryption oracle in logging_ctl::logging_more(), implement unique cryptographic keys for UCenter integration versus database backup functions, add proper authentication enforcement to dbbak.php endpoints, and implement race condition protection for user impersonation vectors.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Discuz! X5.0 version
    Locate the version file (typically version.php or similar in the root directory) and read the version string. Common paths: ./version.php, ./include/version.php, or check the admin panel System > Basic Settings for version information.
    Affected if The installed version falls between 20260320 and 20260501 inclusive.
  2. Locate and verify dbbak.php presence
    Check for the existence of dbbak.php in the web root or common plugin directories (e.g., ./source/plugin/dbbak/, ./api/dbbak.php, or ./utility/dbbak.php).
    Affected if The file dbbak.php exists and is accessible via the web server.
  3. Check UCenter integration status
    Examine the UCenter configuration file (typically ./config/config_ucenter.php or ./uc_client/config.php) and look for UC_KEY or API authentication settings. Verify if UCenter is enabled in admin panel > App > UCenter integration.
    Affected if UCenter integration is enabled and configured with a shared key.
  4. Examine logging_ctl::logging_more() for encryption oracle
    Locate the logging controller (typically in ./source/class/table/table_common_member_login.php or ./source/module/member/login.php) and inspect the logging_more() function for logic that handles username parameter encryption or logging without proper validation.
    Affected if The logging_more() function processes username input in a way that could leak encrypted tokens or serve as an oracle.
  5. Inspect cryptographic key configuration
    Review configuration files for shared or duplicate keys used across UCenter (UC_KEY) and database backup functions (e.g., DBbak auth keys in config or plugin settings). Compare key values to determine if they are identical.
    Affected if The same cryptographic key is used for both UCenter authentication and database backup API operations.

A system is affected if it runs Discuz! X5.0 between versions 20260320-20260501, has accessible dbbak.php, has UCenter integration enabled, contains the vulnerable logging_more() encryption oracle, and uses a shared cryptographic key between UCenter and database backup functions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable the encryption oracle in logging_ctl::logging_more(), implement unique cryptographic keys for UCenter integration versus database backup functions, add proper authentication enforcement to dbbak.php endpoints, and implement race condition protection for user impersonation vectors.

Have this fixed Scoped from the published advisory
  • Consultation6.0 h
  • Implementation20.0 h
  • Testing10.0 h
  • Review / QA6.0 h
42.0 hours of engineering $7,380
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-49952 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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