Vulnerability · Published May 26, 2026 · Assigned by mitre
CVE-2026-48683
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 26% 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 vulnerability in the NetFlow v9 data flowset processor. In src/netflow_plugin/netflow_v9_collector.cpp, the Data template branch (lines 1695-1702) iterates over flow records without performing a per-iteration bounds check against the packet end pointer. In contrast, the Options template branch (lines 1709-1719) correctly checks 'if (pkt + offset + field_template->total_length > packet_end)' before each iteration. The Data branch omits this check entirely. Since template definitions are sent by the network peer (and are unauthenticated UDP), an attacker can craft templates that cause the parser to read arbitrary memory past the packet buffer. This can leak sensitive memory contents or cause a crash.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | fastnetmon | no fix listed | DEBIAN-CVE-2026-48683 |
| Debian:13 | fastnetmon | 1.2.9-0+deb13u1 | DEBIAN-CVE-2026-48683 |
| Debian:14 | fastnetmon | 1.2.9-1 | DEBIAN-CVE-2026-48683 |
| Ubuntu:25.10 | fastnetmon | no fix listed | UBUNTU-CVE-2026-48683 |
| Ubuntu:26.10 | fastnetmon | no fix listed | UBUNTU-CVE-2026-48683 |
Affected products (as reported)
Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N