# CVE-2026-4638: Plaintext Password Disclosure via VBScript Sensor Error Message in Paessler PRTG Network Monitor

> Authenticated users can expose plaintext Windows passwords by triggering a VBScript error in a demo sensor, requiring an upgrade to PRTG Network Monitor.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Sep 2026
- **Updated:** 24 Sep 2026
- **Also known as:** GHSA-gh9q-9rjg-9rq2

## What is CVE-2026-4638?

CVE-2026-4638 is a high-severity vulnerability in Paessler GmbH PRTG Network Monitor, published on 24 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

PRTG Network Monitor before version 26.2.120.1449 ships a demo EXE/Script sensor that multiplies two integer parameters using cscript.exe. If a non-numeric value is passed instead, cscript.exe raises a 'Type mismatch' runtime error that includes the offending parameter value in plaintext. PRTG provides a documented placeholder variable, %windowspassword, which resolves to the configured Windows/domain password used by PRTG and can be passed as a sensor parameter. 

Any PRTG user who is not restricted to read-only access and is permitted to create sensors (the default for non-read-only users) can pass %windowspassword as an argument to the demo VBScript sensor, triggering the type-mismatch error and causing PRTG to display the plaintext password in the sensor's error output.

Weakness: CWE-209 (Generation of Error Message Containing Sensitive Information)

## Which versions are affected by CVE-2026-4638?


## How do I fix CVE-2026-4638?

No fix has been published for CVE-2026-4638 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-4638 being exploited?

There is no known exploitation of CVE-2026-4638 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4638 and fix it if it is affected.

What it is: CVE-2026-4638 is a high-severity vulnerability in Paessler GmbH PRTG Network Monitor, published on 24 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-4638 in the wild and no public exploit code.

Affected product: Paessler GmbH PRTG Network Monitor. 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-2026-4638/ (Markdown: https://insights.sbomify.com/CVE-2026-4638/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4638
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4638
- OSV: https://osv.dev/vulnerability/CVE-2026-4638

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-4638/
Summaries are generated and may contain mistakes; the official description above is the record.