# CVE-2026-11857: Insecure .NET Remoting deserialization in Quanos SCHEMA ST4 Client Update Service allows local privilege escalation

> Local attackers can exploit insecure .NET Remoting deserialization in the update service to execute arbitrary code with SYSTEM privileges.

- **Severity:** High 8.4 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Jun 2026
- **Updated:** 17 Jun 2026
- **Also known as:** GHSA-fmx7-jmr3-4jw2

## What is CVE-2026-11857?

CVE-2026-11857 is a high-severity unsafe deserialization vulnerability in Quanos Solutions GmbH SCHEMA ST4, published on 17 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-11857?


## How do I fix CVE-2026-11857?

No fix has been published for CVE-2026-11857 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-11857 being exploited?

There is no known exploitation of CVE-2026-11857 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11857 and fix it if it is affected.

What it is: CVE-2026-11857 is a high-severity unsafe deserialization vulnerability in Quanos Solutions GmbH SCHEMA ST4, published on 17 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-11857 in the wild and no public exploit code.

Affected product: Quanos Solutions GmbH SCHEMA ST4. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-11857/ (Markdown: https://insights.sbomify.com/CVE-2026-11857/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11857
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11857
- OSV: https://osv.dev/vulnerability/CVE-2026-11857

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-11857/
Summaries are generated and may contain mistakes; the official description above is the record.