FastNetMon Community Edition versions up to 1.2.9 contain a flaw in the NetFlow v9 options template parser that allows an attacker to read data beyond the bounds of a UDP packet. The parser loops over option scopes and values without validating the lengths, enabling a crafted packet to trigger memory over‑reads. An attacker may be able to disclose contents of memory adjacent to the packet buffer, potentially exposing sensitive data within the running system. The vulnerability is a classic buffer over‑read, classified by CWE-125.

Systems running FastNetMon Community Edition before version 1.3.0 are vulnerable, specifically collectors that accept NetFlow v9 traffic over UDP. This includes any deployment that uses the default configuration for NetFlow v9 processing. Users should verify the exact version; versions 1.2.9 and earlier are affected.

No CVSS score is currently assigned and the EPSS score is not available, so the quantified risk level is unclear. However the vulnerability is remotely exploitable over the network using crafted UDP packets and can be triggered without user interaction. The lack of an official CISA KEV listing does not diminish the potential for abuse in environments that use NetFlow v9. Organizations should treat this as a medium‑to‑high risk until an official fix is released. The exploitation complexity appears low for an attacker who can send traffic to the collector’s UDP port.