# CVE-2026-11858: Missing authorization in Quanos SCHEMA ST4 Client Update Service allows arbitrary file overwrite as SYSTEM

> A local attacker can exploit missing authorization in the SCHEMA ST4 Client Update Service to overwrite files and escalate privileges to SYSTEM.

- **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-62mq-g5fg-59fx

## What is CVE-2026-11858?

CVE-2026-11858 is a high-severity missing authorization 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. 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.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-11858?


## How do I fix CVE-2026-11858?

No fix has been published for CVE-2026-11858 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-11858 being exploited?

There is no known exploitation of CVE-2026-11858 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11858 and fix it if it is affected.

What it is: CVE-2026-11858 is a high-severity missing authorization 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-2026-11858 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-2026-11858/ (Markdown: https://insights.sbomify.com/CVE-2026-11858/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11858
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11858
- OSV: https://osv.dev/vulnerability/CVE-2026-11858

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-11858/
Summaries are generated and may contain mistakes; the official description above is the record.