CVE-2026-11858

Missing authorization in Quanos SCHEMA ST4 Client Update Service allows arbitrary file overwrite as SYSTEM

Published Jun 17, 2026 CVSS 4.0 · 8.4 High EPSS < 1% KEV · Not listed
Description
Quanos SCHEMA ST4 on-premises contains a local privilege escalation vulnerability in the Client Update Service. The update service runs as NT AUTHORITY\SYSTEM and exposes a .NET Remoting interface over a named pipe without sufficient access controls or authorization. A local authenticated low-privileged user can connect to the interface and invoke privileged update methods such as Update(). This allows arbitrary file write and delete operations with SYSTEM privileges and can be used to achieve local privilege escalation.

Remediation

Vendor Solution

The vendor does not provide a patch. The vendor recommends disabling the affected Client Update Service. Updating the client is then only possible manually with a privileged user account. Quanos confirms that exploitation requires local host access with an authenticated user session. In properly managed environments following the Least Privilege principle, the attack surface is significantly reduced. Quanos Cloud/SaaS deployments are not affected. Quanos considers the migration to the Cloud/SaaS architecture the strategic long-term solution.


Vendor Workaround

Disable the Client Update Service until a fix is provided. Restrict local interactive access to systems running SCHEMA ST4 on-premises. Apply the principle of least privilege to local user accounts and prevent untrusted users from obtaining local sessions on affected hosts. Ensure that only trusted administrators can perform client updates manually.

Tracking

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Advisories

No advisories available
References
History
Type Values Removed Values Added
First Time appeared Quanos Solutions
Quanos Solutions schema St4
Vendors & Products Quanos Solutions
Quanos Solutions schema St4
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Quanos SCHEMA ST4 on-premises contains a local privilege escalation vulnerability in the Client Update Service. The update service runs as NT AUTHORITY\SYSTEM and exposes a .NET Remoting interface over a named pipe without sufficient access controls or authorization. A local authenticated low-privileged user can connect to the interface and invoke privileged update methods such as Update(). This allows arbitrary file write and delete operations with SYSTEM privileges and can be used to achieve local privilege escalation.
Title Missing authorization in Quanos SCHEMA ST4 Client Update Service allows arbitrary file overwrite as SYSTEM
Weaknesses CWE-862
References
Metrics cvssV4_0

{'score': 8.4, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
SEC-VLab
Published
Updated
Jun 17, 2026, 2:56 PM
Reserved
Jun 10, 2026, 9:08 AM
Status
Deferred
Published
Jun 17, 2026, 1:19 PM
Modified
Oct 26, 2026, 12:10 PM