Auth bypass in widely-deployed Plesk multi-tenant control panel enables cross-tenant FTP credential disclosure and code execution; high-impact for hosting providers and many customer sites.
CVE-2026-56843
Auth bypass in Plesk XML-RPC allows cross-tenant FTP creds disclosure and RCE.
Is CVE-2026-56843 being exploited?
Not confirmed. CVE-2026-56843 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.66% probability of exploitation in the next 30 days.
How severe is CVE-2026-56843?
CVE-2026-56843 is rated Critical with a CVSS score of 9.9. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-56843?
Yes. A fix has been recorded for CVE-2026-56843. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-56843 affect?
CVE-2026-56843 affects WebPros Plesk < 18.0.78.4, Plesk XML-RPC API, Multi-tenant/shared hosting panels using Plesk. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-56843?
Upgrade Plesk to 18.0.78.4+, rotate exposed FTP credentials, audit access logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated low-privileged tenant can read other tenants' cleartext FTP credentials and execute code as their system user (RCE via compromised FTP account).
Immediate action required
- affected>= 10.4 and < 18.0.78.4
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.