CVE-2026-55182 librenms CVE debrief

Who should care

LibreNMS administrators and security teams responsible for network monitoring systems should assess exposure and apply the patch or compensating controls promptly. This includes reviewing configurations, verifying exposure, and implementing mitigations to prevent exploitation. Security teams should also monitor for suspicious activity and implement additional controls as needed.

Why it matters

CVE-2026-55182 is a high-severity vulnerability in LibreNMS that allows authenticated administrators to execute arbitrary operating-system commands. LibreNMS administrators and security teams should assess exposure and apply the patch or compensating controls promptly.

• Authenticated administrators can execute arbitrary operating-system commands on the LibreNMS host.
• The vulnerability allows for potential lateral movement within the network.
• Verification of exposure and patching are crucial to prevent exploitation.
• Monitoring for suspicious activity is recommended to detect potential attacks.

Technical summary

The Signal alert transport in LibreNMS versions from 21.6.0 up to 26.5.0 is vulnerable to command injection due to insufficient escaping of the signal-cli path and Recipient field. An authenticated administrator can craft a transport entry to execute arbitrary operating-system commands on the LibreNMS host by chaining calls to the bundled composer_wrapper.php script. This vulnerability allows for potential lateral movement within the network and emphasizes the need for prompt verification of exposure and patching. The issue is fixed in version 26.5.0.

Defensive priority

LibreNMS administrators should verify exposure and apply the patch promptly.

Recommended defensive actions

• Verify exposure by checking installed LibreNMS versions and configurations.
• Apply the patch by upgrading to LibreNMS version 26.5.0 or later.
• Monitor for suspicious activity and implement compensating controls if patching is not feasible.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and NVD detail page provide information on the vulnerability, and source references include commits and releases from the LibreNMS project. The vulnerability has been fixed in version 26.5.0, and administrators should verify exposure and apply the patch promptly. Evidence of exploitation attempts may be found in monitoring and detection logs.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.