# CVE-2023-53566: netfilter: nft_set_rbtree: fix null deref on element insertion

> A null pointer dereference in the Linux kernel's netfilter subsystem allows local attackers to cause a system crash via specific set element insertions.

- **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 Oct 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2023-53566, DEBIAN-CVE-2023-53566, GHSA-pcw3-hvmm-479h, UBUNTU-CVE-2023-53566

## What is CVE-2023-53566?

CVE-2023-53566 is a high-severity vulnerability in Linux kernel, published on 4 Oct 2025. 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: nft_set_rbtree: fix null deref on element insertion

There is no guarantee that rb_prev() will not return NULL in nft_rbtree_gc_elem():

general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
 nft_add_set_elem+0x14b0/0x2990
  nf_tables_newsetelem+0x528/0xb30

Furthermore, there is a possible use-after-free while iterating,
'node' can be free'd so we need to cache the next value to use.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2023-53566?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2023-53566?

Apply the vendor's patch.

## Is CVE-2023-53566 being exploited?

There is no known exploitation of CVE-2023-53566 in the wild and no public exploit code.

## 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-2023-53566 and fix it if it is affected.

What it is: CVE-2023-53566 is a high-severity vulnerability in Linux kernel, published on 4 Oct 2025. 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-2023-53566 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-2023-53566/ (Markdown: https://insights.sbomify.com/CVE-2023-53566/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53566
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53566
- OSV: https://osv.dev/vulnerability/CVE-2023-53566

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53566/
Summaries are generated and may contain mistakes; the official description above is the record.