# CVE-2026-48684: fastnetmon: FastNetMon Community Edition through 1.2.9 contains an out-of-bounds read in the NetFlow v9 options template parser

CVE-2026-48684 is fixed in fastnetmon on 1 platform, first by DEBIAN-CVE-2026-48684, released June 24, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-48684
- Priority: Routine
- CVSS: 6.5 (medium)
- EPSS: 0.0026
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 26, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | fastnetmon Debian 13.5 (trixie) | 1.2.9-0+deb13u1 | [DEBIAN-CVE-2026-48684](https://patchblox.com/security/data/fix/linux/debian-cve-2026-48684.md) | Jun 24, 2026 |
| Linux | fastnetmon Debian 14 | 1.2.9-1 | [DEBIAN-CVE-2026-48684](https://patchblox.com/security/data/fix/linux/debian-cve-2026-48684.md) | Jun 24, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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