CVE-2026-48690

01/Description

FastNetMon Community Edition through 1.2.9 contains an integer overflow vulnerability in the packet capture buffer allocation. In src/packet_storage.hpp, the allocate_buffer() function computes memory_size_in_bytes as 'buffer_size_in_packets * (max_captured_packet_size + sizeof(fastnetmon_pcap_pkthdr_t)) + sizeof(fastnetmon_pcap_file_header_t)' using unsigned int (32-bit) arithmetic. With max_captured_packet_size=1500 and sizeof(fastnetmon_pcap_pkthdr_t)=16, each packet requires approximately 1516 bytes. If buffer_size_in_packets exceeds approximately 2,832,542, the multiplication overflows, resulting in a much smaller allocation than expected. Subsequent write_packet() calls then write past the allocated buffer, causing heap corruption. The buffer_size_in_packets value is derived from the ban_details_records_count configuration parameter, which is parsed using atoi() with no overflow checking.

02/Affected products

pavel-odintsov: fastnetmon

03/References3

• github.com/pavel-odintsov/fastnetmon Product
• github.com/pavel-odintsov/fastnetmon/blob/master/src/packet_sto… Product
• lorikeetsecurity.com/blog/fastnetmon-cve-2026-48690-packet-stor… Third Party Advisory