# CVE-2026-23231: netfilter: nf_tables: fix use-after-free in nf_tables_addchain()

> A use-after-free in the Linux kernel's nf_tables allows attackers to potentially execute code or escalate privileges via race conditions during chain registration failures.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Mar 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-78650, BELL-CVE-2026-23231, DEBIAN-CVE-2026-23231, GHSA-gxm6-px42-mpjc, ROOT-OS-DEBIAN-11-CVE-2026-23231, ROOT-OS-DEBIAN-12-CVE-2026-23231, ROOT-OS-DEBIAN-13-CVE-2026-23231, ROOT-OS-UBUNTU-2204-CVE-2026-23231, ROOT-OS-UBUNTU-2404-CVE-2026-23231, UBUNTU-CVE-2026-23231, USN-8254-3

## What is CVE-2026-23231?

CVE-2026-23231 is a high-severity use after free vulnerability in Linux kernel, published on 4 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: fix use-after-free in nf_tables_addchain()

nf_tables_addchain() publishes the chain to table->chains via
list_add_tail_rcu() (in nft_chain_add()) before registering hooks.
If nf_tables_register_hook() then fails, the error path calls
nft_chain_del() (list_del_rcu()) followed by nf_tables_chain_destroy()
with no RCU grace period in between.

This creates two use-after-free conditions:

 1) Control-plane: nf_tables_dump_chains() traverses table->chains
    under rcu_read_lock(). A concurrent dump can still be walking
    the chain when the error path frees it.

 2) Packet path: for NFPROTO_INET, nf_register_net_hook() briefly
    installs the IPv4 hook before IPv6 registration fails.  Packets
    entering nft_do_chain() via the transient IPv4 hook can still be
    dereferencing chain->blob_gen_X when the error path frees the
    chain.

Add synchronize_rcu() between nft_chain_del() and the chain destroy
so that all RCU readers -- both dump threads and in-flight packet
evaluation -- have finished before the chain is freed.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-23231?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23231?

Apply the vendor's patch.

## Is CVE-2026-23231 being exploited?

There is no known exploitation of CVE-2026-23231 in the wild and no public exploit code.

Public exploit code:

- Linux nf_tables 6.19.3 - Local Privilege Escalation (exploitdb)

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23231 and fix it if it is affected.

What it is: CVE-2026-23231 is a high-severity use after free vulnerability in Linux kernel, published on 4 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23231 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-23231/ (Markdown: https://insights.sbomify.com/CVE-2026-23231/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23231
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23231
- OSV: https://osv.dev/vulnerability/CVE-2026-23231

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23231/
Summaries are generated and may contain mistakes; the official description above is the record.