Executive brief
FastNetMon Community Edition, a high-performance DDoS sensor and traffic analyzer, contains a flaw in how it processes NetFlow v9 network traffic data. An attacker can send specially crafted network packets that cause the software to read beyond its intended memory boundaries. This can lead to the exposure of sensitive information from the system's memory or cause the monitoring service to crash, potentially blinding network administrators to ongoing DDoS attacks.
Technical details
An out-of-bounds read vulnerability exists in `src/netflow_plugin/netflow_v9_collector.cpp` within the `process_netflow_v9_data_flowset` function. The 'Data' template branch fails to perform a per-iteration bounds check against the packet end pointer when iterating over flow records, unlike the 'Options' branch which correctly implements this check. Because NetFlow v9 is a template-based protocol sent over unauthenticated UDP, a remote attacker can provide a malicious template definition followed by a truncated data packet. This forces the parser to read past the UDP receive buffer and into adjacent heap memory. An attacker can potentially leak sensitive memory contents (such as BGP state or configuration data) if they can observe the collector's output, or cause a denial-of-service via a segmentation fault.
Affected products
- FastNetMon LTD FastNetMon Community Edition through 1.2.9
Timeline
- 2026-04-25: other: Vulnerability reported to vendor
- 2026-05-23: disclosed: Public disclosure by Lorikeet Security
- 2026-05-26: advisory: CVE published by MITRE/NVD