LibreNMS — Stored XSS via SNMP/Syslog Data in Legacy Templates

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

EPSS

• CVE-2026-84192: 0.33% estimated exploitation activity in the next 30 days; percentile 26.33 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Multiple legacy PHP template files in LibreNMS directly output SNMP-sourced and syslog-sourced data into HTML without escaping. An attacker who controls a monitored network device (via compromised SNMP agent or syslog sender) can inject arbitrary JavaScript that executes when any authenticated LibreNMS user views the affected pages. Vulnerable Code Location 1: Syslog program field (clearest instance) File: includes/html/print-syslog.inc.php:11,13 The program field is output without htmlspecialchars() while the adjacent msg field IS properly escaped. The program value comes from syslog messages received from monitored devices. Location 2: Alert details ifAlias (highest impact — main alerts page) File: includes/html/functions.inc.php:607 The ifAlias (port description) comes from SNMP polling and is stored in the ports table. When a port-related alert fires, formatalertdetails() renders it unescaped. Multiple other fields in this function are also unescaped:…

Published by the source

26 Aug 2026, 18:05 UTC

Last modified by the source

2 Sep 2026, 03:55 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-7w8c-qgxg-m7jx

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-7w8c-qgxg-m7jx

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# Patch Next advisory brief: CVE-2026-84192

Advisory: LibreNMS — Stored XSS via SNMP/Syslog Data in Legacy Templates
IDs: CVE-2026-84192, GHSA-7w8c-qgxg-m7jx
Record: https://patchnext.com/advisories/cve-2026-84192 (revision 2, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: librenms/librenms 26.5.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist librenms/librenms: affected < 26.5.0; fixed in 26.5.0

## Suggested inspection (read-only)
- Packagist librenms/librenms: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on librenms/librenms.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-7w8c-qgxg-m7jx (OSV record GHSA-7w8c-qgxg-m7jx lists affected ranges: Packagist librenms/librenms >=0 <26.5.0 (fixed))
- Verified: https://github.com/advisories/GHSA-7w8c-qgxg-m7jx (GitHub-reviewed advisory GHSA-7w8c-qgxg-m7jx lists affected ranges: Packagist librenms/librenms >=0 <26.5.0)

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