A security flaw has been identified in FastNetMon Community Edition, affecting all versions up to 1.2.9. This is a command injection vulnerability that could allow unauthorized people to run unapproved commands on servers where this software is installed.
The flaw exists in a plugin designed to connect FastNetMon to Juniper routers. The plugin takes input such as IP addresses linked to network activity, traffic direction, and activity strength, and inserts this unsanitized data directly into system commands. While the current core version of FastNetMon only passes safely formatted IP addresses, the plugin has no safeguards against harmful input. If the plugin is called directly by other tools, or if future updates to FastNetMon change how it sends data to the plugin, attackers could inject malicious commands to run on the affected server.
The recommended fix for this issue is to either replace the vulnerable command-running function with a safer file-writing method, or add input sanitization to all parameters passed to the command.
Source: NVD (National Vulnerability Database) — https://nvd.nist.gov/vuln/detail/CVE-2026-48687