# CVE-2021-37220: Memory corruption in n/a

> An out-of-bounds write in MuPDF allows attackers to execute arbitrary code or cause denial of service via crafted input.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 21 Jul 2021
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-37220, GHSA-244v-xghf-wq26, UBUNTU-CVE-2021-37220

## What is CVE-2021-37220?

CVE-2021-37220 is a medium-severity memory corruption vulnerability in Artifex Mupdf, published on 21 Jul 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

MuPDF through 1.18.1 has an out-of-bounds write because the cached color converter does not properly consider the maximum key size of a hash table. This can, for example, be seen with crafted "mutool draw" input.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-37220?

It affects 2 products.


Products: Artifex Mupdf, Fedoraproject Fedora.

## How do I fix CVE-2021-37220?

Upgrade to a fixed version.

## Is CVE-2021-37220 being exploited?

There is no known exploitation of CVE-2021-37220 in the wild and no public exploit code.

## Other vulnerabilities in Artifex Mupdf

- [CVE-2019-7321](https://insights.sbomify.com/CVE-2019-7321/): Memory corruption in n/a (critical 9.8)
- [CVE-2016-6525](https://insights.sbomify.com/CVE-2016-6525/): Memory corruption in n/a (critical 9.8)
- [CVE-2011-0341](https://insights.sbomify.com/CVE-2011-0341/): Memory corruption in n/a (critical 9.3)
- [CVE-2016-8728](https://insights.sbomify.com/CVE-2016-8728/): Memory corruption in MuPDF (high 8.6)
- [CVE-2021-3407](https://insights.sbomify.com/CVE-2021-3407/): Use after free in mupdf (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-37220 and fix it if it is affected.

What it is: CVE-2021-37220 is a medium-severity memory corruption vulnerability in Artifex Mupdf, published on 21 Jul 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-37220 in the wild and no public exploit code.

Affected product: Artifex Mupdf. 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-2021-37220/ (Markdown: https://insights.sbomify.com/CVE-2021-37220/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37220
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37220
- OSV: https://osv.dev/vulnerability/CVE-2021-37220

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-37220/
Summaries are generated and may contain mistakes; the official description above is the record.