# CVE-2023-31248: Linux Kernel nftables Use-After-Free Local Privilege Escalation Vulnerability

> A use-after-free in Linux Kernel nftables allows local attackers to escalate privileges by exploiting missing active chain checks.

- **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:** 5 Jul 2023
- **Updated:** 5 Mar 2025
- **Also known as:** DEBIAN-CVE-2023-31248, GHSA-vr3g-637q-4rh6, UBUNTU-CVE-2023-31248

## What is CVE-2023-31248?

CVE-2023-31248 is a high-severity use after free vulnerability in Canonical Ubuntu Linux, published on 5 Jul 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Linux Kernel nftables Use-After-Free Local Privilege Escalation Vulnerability; `nft_chain_lookup_byid()` failed to check whether a chain was active and CAP_NET_ADMIN is in any user or network namespace

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2023-31248?

It affects 4 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Linux kernel.

## How do I fix CVE-2023-31248?

Apply the vendor's patch.

## Is CVE-2023-31248 being exploited?

There is no known exploitation of CVE-2023-31248 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-31248 and fix it if it is affected.

What it is: CVE-2023-31248 is a high-severity use after free vulnerability in Canonical Ubuntu Linux, published on 5 Jul 2023. 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-2023-31248 in the wild and no public exploit code.

Affected product: Canonical Ubuntu 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-2023-31248/ (Markdown: https://insights.sbomify.com/CVE-2023-31248/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-31248
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-31248
- OSV: https://osv.dev/vulnerability/CVE-2023-31248

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-31248/
Summaries are generated and may contain mistakes; the official description above is the record.