CVE-2026-45694
MEDIUMCVE-2026-45694 is a medium-severity (CVSS 5.4) vulnerability in librenms/librenms. O3 Security confirms whether CVE-2026-45694 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
LibreNMS: Reflected XSS via Proxmox instance/vmid GET parameters injected into document.title JavaScript assignment
Real-World Exposure
librenms/librenmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | librenms/librenms | all versions | 26.5.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for librenms/librenms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update librenms/librenms to 26.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45694 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-45694 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-45694. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-45694 in your dependencies?
O3 detects CVE-2026-45694 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.