FastNetMon Community Edition through version 1.2.9 has an out-of-bounds read vulnerability in its IPv4 packet parser located in src/simple_packet_parser_ng.cpp. After confirming the packet has at least 20 bytes (the minimum IPv4 header size), the code advances a pointer by 4 times the IHL field value without verifying that IHL is at least 5 or that the packet contains sufficient bytes for this advancement. Since IHL is a 4-bit field allowing values from 0 to 15, an attacker can craft packets with invalid IHL values causing the pointer to advance incorrectly, leading to reading beyond the packet buffer or misinterpreting header data. This vulnerability is reachable through any packet capture interface and can cause memory safety issues classified as CWE-125 (Out-of-bounds Read).

An attacker can send specially crafted IPv4 packets that exploit the improper validation of the IHL field, causing the application to read memory beyond the intended buffer boundaries. This may lead to disclosure of sensitive information from adjacent memory areas (confidentiality impact). There is no indication of integrity or availability impact. No known exploits are reported in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid processing untrusted IPv4 packets or restrict packet capture interfaces to trusted sources. Monitor vendor channels for updates or official patches addressing this vulnerability.