CVE-2026-48690 describes an integer overflow vulnerability in FastNetMon Community Edition (up to 1.2.9) within the allocate_buffer() function in src/packet_storage.hpp. The function calculates the required memory size for packet capture buffers using 32-bit unsigned integer arithmetic. When the buffer_size_in_packets parameter exceeds approximately 2,832,542, the multiplication overflows, resulting in a smaller allocated buffer than intended. Subsequent write operations then corrupt the heap. The buffer_size_in_packets is derived from the ban_details_records_count configuration parameter, which is parsed using atoi() without overflow checking, enabling this condition.

Heap corruption caused by writing beyond the allocated buffer can lead to application instability, crashes, or potentially exploitable conditions. However, there are no known exploits in the wild and no CVSS score or detailed impact assessment is provided. The vulnerability could be leveraged to disrupt FastNetMon operations or possibly execute arbitrary code if exploited.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should avoid configuring excessively large values for ban_details_records_count that could trigger the integer overflow. Monitoring vendor communications for updates is recommended.