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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
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.
Sources
Also known as GHSA-gh9q-9rjg-9rq2.