Vulnerability · Published May 26, 2026 · Assigned by mitre
CVE-2026-48684
Medium 6.5
In plain English
A medium-severity out-of-bounds read 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 0.3% (higher than 18% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
FastNetMon Community Edition through 1.2.9 contains an out-of-bounds read in the NetFlow v9 options template parser. In process_netflow_v9_options_template() (src/netflow_plugin/netflow_v9_collector.cpp), the scope parsing loop (lines 224-229) iterates until scopes_offset reaches the attacker-controlled option_scope_length value, reading netflow9_template_flowset_record_t structures at each step. No bounds check validates that (zone_address + scopes_offset + sizeof(record)) stays within the flowset. The same issue affects the options field loop (lines 241-257) with option_length. Furthermore, option_scope_length is not validated to be a multiple of sizeof(netflow9_template_flowset_record_t), potentially causing misaligned reads. An attacker can trigger reads past the end of the UDP packet buffer.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | fastnetmon | no fix listed | DEBIAN-CVE-2026-48684 |
| Debian:13 | fastnetmon | 1.2.9-0+deb13u1 | DEBIAN-CVE-2026-48684 |
| Debian:14 | fastnetmon | 1.2.9-1 | DEBIAN-CVE-2026-48684 |
| Ubuntu:25.10 | fastnetmon | no fix listed | UBUNTU-CVE-2026-48684 |
| Ubuntu:26.10 | fastnetmon | no fix listed | UBUNTU-CVE-2026-48684 |
Affected products (as reported)
Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L