Insecure .NET Remoting deserialization in Quanos SCHEMA ST4 Client Update Service allows local privilege escalation
Summary
| CVE | CVE-2026-11857 |
|---|---|
| State | PUBLISHED |
| Assigner | SEC-VLab |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-06-17 13:19:33 UTC |
| Updated | 2026-06-17 16:21:32 UTC |
| Description | Quanos SCHEMA ST4 on-premises contains a local privilege escalation vulnerability in the Client Update Service due to insecure deserialization in the .NET Remoting service. The service is configured with TypeFilterLevel.Full and is bound to local interfaces only through named pipes. A local authenticated attacker can connect to the local named pipe, obtain the .NET Remoting endpoint, and send specially crafted serialized objects. Successful exploitation results in arbitrary code execution in the context of the update process with NT AUTHORITY\SYSTEM privileges. Network-only exploitation is not possible and local host access with an authenticated user session is required. |
Risk And Classification
Primary CVSS: v4.0 8.4 HIGH from 551230f0-3615-47bd-b7cc-93e92e730bbf
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.002730000 probability, percentile 0.188510000 (date 2026-06-23)
Problem Types: CWE-502 | CWE-502 CWE-502 Deserialization of untrusted data
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 551230f0-3615-47bd-b7cc-93e92e730bbf | Secondary | 8.4 | HIGH | 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/E:X/C... |
| 4.0 | CNA | CVSS | 8.4 | HIGH | 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 |
CVSS v4.0 Breakdown
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Quanos Solutions GmbH | SCHEMA ST4 | affected SCHEMA ST4 on-premises, all versions custom | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| r.sec-consult.com/quanos | 551230f0-3615-47bd-b7cc-93e92e730bbf | r.sec-consult.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Johannes Kruchem, SEC Consult Vulnerability Lab (en)
Additional Advisory Data
Solutions
CNA: 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.
Workarounds
CNA: 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.