CVE-2026-55182

Received Received - Intake

Command Injection in LibreNMS Alert Transport

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: GitHub, Inc.

Description

LibreNMS is a network monitoring system. In versions from 21.6.0 up to 26.5.0, the Signal alert transport is vulnerable to command injection because the signal-cli path and the Recipient field of an alert transport entry are insufficiently escaped before being passed to an exec call. An authenticated administrator can craft a transport entry whose Recipient contains shell metacharacters and whose path points to the bundled composer_wrapper.php script, which itself passes attacker-controlled input to further unsafe exec calls. By chaining these calls, the administrator can execute arbitrary operating-system commands on the LibreNMS host. This issue is fixed in version 26.5.0.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-26

Last Modified

2026-08-26

Generated

2026-08-27

AI Q&A

2026-08-27

EPSS Evaluated

N/A

NVD

CVE-2026-55182

Affected Vendors & Products

Vendor	Product	Version / Range
librenms	librenms	From 21.6.0 (inc) to 26.5.0 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-77	The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

Attack-Flow Graph

Executive Summary

LibreNMS versions 21.6.0 to 26.5.0 have a command injection flaw in the Signal alert transport. The issue occurs because the signal-cli path and Recipient field are not properly escaped before being passed to an exec call. An authenticated admin can exploit this by crafting a transport entry with shell metacharacters in the Recipient field and a path pointing to composer_wrapper.php, which then executes arbitrary OS commands on the host.

Detection Guidance

Check LibreNMS versions between 21.6.0 and 26.5.0 by running: grep -r 'version' /opt/librenms/config.php or check the web interface footer. Inspect alert transport settings for suspicious Signal transport entries with unusual paths or recipients containing shell metacharacters.

Impact Analysis

This vulnerability allows an authenticated administrator to execute arbitrary commands on the LibreNMS server. This could lead to full system compromise, unauthorized data access, or disruption of network monitoring services. Attackers could install malware, steal sensitive data, or pivot to other systems in the network.

Compliance Impact

This vulnerability could lead to unauthorized access or data breaches, violating GDPR and HIPAA requirements for data protection and access controls. Organizations using affected LibreNMS versions may face compliance violations, legal penalties, and reputational damage if exploited.

Mitigation Strategies

Upgrade LibreNMS to version 26.5.0 or later immediately. If immediate upgrade is not possible, disable the Signal alert transport feature in the admin panel or remove the vulnerable composer_wrapper.php script. Review all alert transport configurations for unauthorized changes.

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