# CVE-2025-66266: Insecure SYSTEM Service Permissions in UPSilon2000V6.0 (RupsMon.exe) leading to trivial Local Privilege Escalation

> Local attackers can escalate privileges to SYSTEM by replacing the RupsMon.exe service executable due to insecure file permissions.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 Nov 2025
- **Updated:** 26 Nov 2025
- **Also known as:** GHSA-9553-998g-436x

## What is CVE-2025-66266?

CVE-2025-66266 is a critical vulnerability in MegaTec Taiwan UPSilon2000V6.0, published on 26 Nov 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The RupsMon.exe service executable in UPSilon 2000 has insecure permissions, allowing the 'Everyone' group Full Control. A local attacker can replace the executable with a malicious binary to execute code with SYSTEM privileges or simply change the config path of the service to a command; starting and stopping the service to immediately achieve code execution and privilege escalation

Weakness: CWE-269 (Improper Privilege Management)

## Which versions are affected by CVE-2025-66266?


## How do I fix CVE-2025-66266?

No fix has been published for CVE-2025-66266 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-66266 being exploited?

There is no known exploitation of CVE-2025-66266 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66266 and fix it if it is affected.

What it is: CVE-2025-66266 is a critical vulnerability in MegaTec Taiwan UPSilon2000V6.0, published on 26 Nov 2025. 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-2025-66266 in the wild and no public exploit code.

Affected product: MegaTec Taiwan UPSilon2000V6.0. 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-2025-66266/ (Markdown: https://insights.sbomify.com/CVE-2025-66266/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66266
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66266
- OSV: https://osv.dev/vulnerability/CVE-2025-66266

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-66266/
Summaries are generated and may contain mistakes; the official description above is the record.