Open-Source Security Intelligence

Know every vulnerability
before it knows you.

DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.

Checkout DevGuardView on GitHub
Search

GHSA-jmqm-f8q4-v7wx

MediumCVSS 5.4 / 10
Published Aug 12, 2026·Last modified Aug 12, 2026
Affected Components(1)
Packagist logolibrenms/librenms
< 26.5.0
Description

Summary

LegacyController.php:75 writes the page title into a document.title JS assignment using string interpolation. apps/proxmox.inc.php pushes $vars['instance'] and $vars['vmid'] (GET params, only strip_tags() applied) directly into $pagetitle. A single quote terminates the JS string, executing arbitrary script.

Details

// LegacyController.php:75
$html .= "<script>\ndocument.title = '$title';\n</script>";

// proxmox.inc.php:38,42
$pagetitle[] = $instance;     // GET ?instance=
$pagetitle[] = $vars['vmid']; // GET ?vmid=

PoC

http://target/apps?app=proxmox&instance=%27%3Balert%28document.cookie%29%3B//

Confirmed in response:
document.title = 'Apps - Proxmox - ';alert(document.cookie);// - LibreNMS';

Fix

// LegacyController.php:75
$html .= "<script>\ndocument.title = " . json_encode($title) . ";\n</script>";

Also wrap $instance and $vars['vmid'] in htmlspecialchars() in proxmox.inc.php.

Prerequisite

Any authenticated session. Victim must follow a crafted link.

Risk Scores
Base Score
5.4

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
5.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

Related Vulnerabilities
  • CVE-2026-45694
    Alias

Browse More

Medium severity
Scan your project

Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.

Checkout DevGuard