Vulnerability · Published May 26, 2026 · Assigned by mitre
CVE-2026-48690
High 7.1
In plain English
A high-severity integer overflow in the fastnetmon package (Debian). There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | fastnetmon | no fix listed | DEBIAN-CVE-2026-48690 |
| Debian:13 | fastnetmon | 1.2.9-0+deb13u1 | DEBIAN-CVE-2026-48690 |
| Debian:14 | fastnetmon | 1.2.9-1 | DEBIAN-CVE-2026-48690 |
| Ubuntu:25.10 | fastnetmon | no fix listed | UBUNTU-CVE-2026-48690 |
| Ubuntu:26.10 | fastnetmon | no fix listed | UBUNTU-CVE-2026-48690 |
Affected products (as reported)
Weakness: CWE-190, CWE-122 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N