CyberSecBulletin
CVE-2026-56843NVD status: Deferred

Plesk: Insufficiently Protected Credentials

Published Updated By the CyberSecBulletin desk

CVE-2026-56843 is a critical-severity insufficiently protected credentials vulnerability in Plesk from WebPros, with a CVSS 3.1 base score of 9.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 18.0.78.4 as the first without the flaw, so updating Plesk to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Plesk to 18.0.78.4 or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
WebprosPlesk10.4 up to, but not including, 18.0.78.418.0.78.4

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (hackerone.com).

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Insufficiently Protected Credentials

The product transmits or stores authentication credentials, but it uses an insecure method that is susceptible to unauthorized interception and/or retrieval.

How developers prevent this class of flaw

  • Use an appropriate security mechanism to protect the credentials.
  • Make appropriate use of cryptography to protect the credentials.
  • Use industry standards to protect the credentials (e.g. LDAP, keystore, etc.).

More Insufficiently Protected Credentials vulnerabilities (CWE-522)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Plesk

All Plesk vulnerabilities

Recent Insufficiently Protected Credentials vulnerabilities

Spotted an error? Tell us.