# CVE-2022-3620: Exim DMARC dmarc.c dmarc_dns_lookup use after free

> Remote attackers can exploit a use-after-free flaw in Exim's DMARC handler to potentially execute code or cause a denial of service.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Oct 2022
- **Updated:** 15 Apr 2025
- **Also known as:** DEBIAN-CVE-2022-3620, GHSA-jcq6-47h7-2c66

## What is CVE-2022-3620?

CVE-2022-3620 is a medium-severity use after free vulnerability in Exim Exim, published on 20 Oct 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was found in Exim and classified as problematic. This issue affects the function dmarc_dns_lookup of the file dmarc.c of the component DMARC Handler. The manipulation leads to use after free. The attack may be initiated remotely. The name of the patch is 12fb3842f81bcbd4a4519d5728f2d7e0e3ca1445. It is recommended to apply a patch to fix this issue. The associated identifier of this vulnerability is VDB-211919.

Weakness: CWE-416 (Use After Free), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2022-3620?

It affects 2 products.


Products: Exim Exim, Fedoraproject Fedora.

## How do I fix CVE-2022-3620?

Apply the vendor's patch.

## Is CVE-2022-3620 being exploited?

There is no known exploitation of CVE-2022-3620 in the wild and no public exploit code.

## Other vulnerabilities in Exim Exim

- [CVE-2026-45185](https://insights.sbomify.com/CVE-2026-45185/): Use after free in Exim (critical 9.8)
- [CVE-2023-42115](https://insights.sbomify.com/CVE-2023-42115/): Exim AUTH Out-Of-Bounds Write Remote Code Execution Vulnerability (critical 9.8)
- [CVE-2020-28017](https://insights.sbomify.com/CVE-2020-28017/): Integer overflow in n/a (critical 9.8)
- [CVE-2020-28018](https://insights.sbomify.com/CVE-2020-28018/): Use after free in n/a (critical 9.8)
- [CVE-2020-28020](https://insights.sbomify.com/CVE-2020-28020/): Integer overflow in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-3620 and fix it if it is affected.

What it is: CVE-2022-3620 is a medium-severity use after free vulnerability in Exim Exim, published on 20 Oct 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2022-3620 in the wild and no public exploit code.

Affected product: Exim Exim. 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-2022-3620/ (Markdown: https://insights.sbomify.com/CVE-2022-3620/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-3620
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-3620
- OSV: https://osv.dev/vulnerability/CVE-2022-3620

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-3620/
Summaries are generated and may contain mistakes; the official description above is the record.