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Insufficiently Protected CredentialsWeakness · CWE-522

CVE-2026-56843

CRITICAL · 9.9 CVSS v3.1 Published 2026-07-08
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 Zero-click 7 weeks old

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
Incorrect authorization in the XML-RPC API of WebPros Plesk before 18.0.78.4 allows a low-privileged authenticated customer to look up domains they do not own, because ownership is enforced only for certain lookup filters and schema validation is bypassed for legacy protocol versions. This results in cross-tenant disclosure of other tenants' FTP credentials stored in cleartext, which can be leveraged to execute code as another tenant's system user.

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

The XML-RPC API in Plesk versions before 18.0.78.4 fails to consistently enforce domain ownership authorization. Low-privileged customer accounts can bypass ownership checks by using certain lookup filters or legacy protocol versions where schema validation is bypassed, enabling unauthorized access to other tenants' domains and their FTP credentials stored in cleartext.

MitigationUpgrade Plesk to version 18.0.78.4 or later to obtain the vendor patch that enforces ownership consistently across all API filters and protocol versions.

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
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

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

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. Determine Plesk installation version
    Run 'plesk version' from command line or check the version displayed in Plesk admin interface under Server Information
    Affected if Installed version is earlier than 18.0.78.4 (e.g., 18.0.78.3, 18.0.78.2, etc.)
  2. Confirm XML-RPC API is accessible
    Verify the XML-RPC endpoint responds to requests (typically at /enterprise/control/agent.php or /rpc/); check if the API port/service is open
    Affected if XML-RPC API is enabled and reachable, and the Plesk version is below 18.0.78.4
  3. Audit API access logs for cross-tenant domain queries
    Search Plesk logs (typically in /var/log/plesk/) for API calls that retrieve domain information from other customer accounts; look for API actions like 'domain-get' or 'domain-info' where the requesting customer differs from the domain owner
    Affected if Logs show low-privileged accounts successfully querying domains owned by different customer accounts, and version is before 18.0.78.4
  4. Review API logs for FTP credential exposure attempts
    Inspect API access logs for requests that retrieve FTP credentials (action 'ftp-user-get' or similar) for domains owned by other tenants
    Affected if Logs contain FTP credential retrievals by customers for domains they do not own, and version is vulnerable

A Plesk installation is affected if it runs a version before 18.0.78.4 and has the XML-RPC API enabled, with evidence of cross-tenant domain or FTP credential access by low-privileged accounts.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Plesk to version 18.0.78.4 or later to obtain the vendor patch that enforces ownership consistently across all API filters and protocol versions.

Recommended fix Moderate confidence

Plesk 18.0.78.4 or later

  1. 1. Backup the current Plesk installation and all customer data before proceeding with any upgrade.
  2. 2. Review the Plesk upgrade documentation for your current version at support.plesk.com.
  3. 3. Ensure all system prerequisites are met for upgrading to Plesk 18.0.78.4 or later.
  4. 4. Perform the upgrade to Plesk version 18.0.78.4 or the latest stable release available.
  5. 5. After upgrading, verify that the XML-RPC API authorization controls are functioning correctly by testing cross-tenant domain lookups.
  6. 6. Confirm that low-privileged customers can no longer access domains they do not own.
  7. 7. Validate that FTP credentials for other tenants are no longer exposed through the API.
Caveat Upgrading Plesk may affect existing extensions, custom configurations, or legacy API integrations; test in a staging environment first

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,900
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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-2026-56843 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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