Description
LibreNMS is a network monitoring system. In versions up to and including 26.4.0, the Proxmox application view is vulnerable to reflected cross-site scripting through the user-supplied instance and vmid GET parameters, which are reflected into the page title without adequate encoding. The parameters are placed into the page title with only strip_tags applied, and the title is then written into an inline document.title assignment through string interpolation, so a single quote terminates the JavaScript string and the remaining input runs as script. An attacker who lures an authenticated user into following a crafted link can execute script in that user's session, enabling actions such as theft of session data. This issue is fixed in version 26.5.0.
References2
Metrics
- CVSS 3.1
-
5.4
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N - EPSS — exploit probability
- 0% percentile: 14 · as of 9 November 2026
- CWE
- CWE-79
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.