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GHSA-jmqm-f8q4-v7wxmedium5.4

LibreNMS: Reflected XSS via Proxmox instance/vmid GET parameters injected into document.title JavaScript assignment

Impact

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.

Source excerpt · OSV

Affected packages

Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.

librenms/librenms Packagist
Affected rangeRecorded fix
Earlier releases before 26.5.0Ecosystem versions26.5.0

Version evidence: OSV · GHSA-jmqm-f8q4-v7wx

View original version evidence (154 explicit versions)

Original source 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.

References