# CVE-2023-42756: Kernel: netfilter: race condition between ipset_cmd_add and ipset_cmd_swap

> A local attacker can trigger a race condition in the Linux kernel netfilter subsystem to cause a system crash.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Sep 2023
- **Updated:** 6 Nov 2025
- **Also known as:** AZL-30055, BELL-CVE-2023-42756, DEBIAN-CVE-2023-42756, GHSA-9fpq-xxr8-j37x, UBUNTU-CVE-2023-42756

## What is CVE-2023-42756?

CVE-2023-42756 is a medium-severity vulnerability in Debian Debian Linux, published on 28 Sep 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in the Netfilter subsystem of the Linux kernel. A race condition between IPSET_CMD_ADD and IPSET_CMD_SWAP can lead to a kernel panic due to the invocation of `__ip_set_put` on a wrong `set`. This issue may allow a local user to crash the system.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2023-42756?

It affects 4 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Linux kernel, Redhat Enterprise Linux.

## How do I fix CVE-2023-42756?

Apply the vendor's patch.

## Is CVE-2023-42756 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-42756 exists.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-42756 and fix it if it is affected.

What it is: CVE-2023-42756 is a medium-severity vulnerability in Debian Debian Linux, published on 28 Sep 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-42756 exists.

Affected product: Debian Debian Linux. 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-2023-42756/ (Markdown: https://insights.sbomify.com/CVE-2023-42756/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-42756
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-42756
- OSV: https://osv.dev/vulnerability/CVE-2023-42756

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-42756/
Summaries are generated and may contain mistakes; the official description above is the record.