LibreNMS up to 26.4.0 Proxmox Application View instance/vmid cross site scripting

Summaryinfo

A vulnerability described as problematic has been identified in LibreNMS up to 26.4.0. Impacted is an unknown function of the component Proxmox Application View. Executing a manipulation of the argument instance/vmid can lead to cross site scripting. This vulnerability is handled as CVE-2026-45694. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in LibreNMS up to 26.4.0. It has been declared as problematic. This vulnerability affects an unknown code block of the component Proxmox Application View. The manipulation of the argument instance/vmid with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-45694 since 05/13/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 26.5.0 eliminates this vulnerability.

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Productinfo

Name

• LibreNMS

Version

• 26.0
• 26.1
• 26.2
• 26.3
• 26.4.0

License

• open-source

Website

• Product: https://github.com/librenms/librenms/

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