# CVE-2020-36694: Use after free in n/a

> A use-after-free in the Linux kernel netfilter allows local attackers with CAP_NET_ADMIN to execute code or escalate privileges.

- **Severity:** Medium 6.7 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/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:** 21 May 2023
- **Updated:** 31 Jan 2025
- **Also known as:** DEBIAN-CVE-2020-36694, GHSA-7prr-xcc8-8wpv, ROOT-OS-DEBIAN-11-CVE-2020-36694, ROOT-OS-DEBIAN-12-CVE-2020-36694, ROOT-OS-DEBIAN-13-CVE-2020-36694, UBUNTU-CVE-2020-36694

## What is CVE-2020-36694?

CVE-2020-36694 is a medium-severity use after free vulnerability in Linux kernel, published on 21 May 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An issue was discovered in netfilter in the Linux kernel before 5.10. There can be a use-after-free in the packet processing context, because the per-CPU sequence count is mishandled during concurrent iptables rules replacement. This could be exploited with the CAP_NET_ADMIN capability in an unprivileged namespace. NOTE: cc00bca was reverted in 5.12.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2020-36694?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2020-36694?

Apply the vendor's patch.

## Is CVE-2020-36694 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-36694 exists.

## 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-2020-36694 and fix it if it is affected.

What it is: CVE-2020-36694 is a medium-severity use after free vulnerability in Linux kernel, published on 21 May 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-2020-36694 exists.

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-2020-36694/ (Markdown: https://insights.sbomify.com/CVE-2020-36694/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-36694
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-36694
- OSV: https://osv.dev/vulnerability/CVE-2020-36694

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-36694/
Summaries are generated and may contain mistakes; the official description above is the record.