# CVE-2021-20176: Denial of service in ImageMagick

> An attacker can cause a denial of service in ImageMagick by submitting a crafted file that triggers a divide-by-zero error.

- **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:** 5 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** CVE-2021-20242, DEBIAN-CVE-2021-20176, GHSA-rjh9-hq94-crmg, JLSEC-2026-877, SUSE-SU-2021:3996-1, UBUNTU-CVE-2021-20176, openSUSE-SU-2021:1583-1, openSUSE-SU-2021:3996-1

## What is CVE-2021-20176?

CVE-2021-20176 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 5 Feb 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

A divide-by-zero flaw was found in ImageMagick 6.9.11-57 and 7.0.10-57 in gem.c. This flaw allows an attacker who submits a crafted file that is processed by ImageMagick to trigger undefined behavior through a division by zero. The highest threat from this vulnerability is to system availability.

Weakness: CWE-369 (Divide By Zero)

## Which versions are affected by CVE-2021-20176?

It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ImageMagick` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP2 | All versions | 7.0.7.34-10.18.1 |
| `ImageMagick` | SUSE:Linux Enterprise Module for Desktop Applications 15 SP3 | All versions | 7.0.7.34-10.18.1 |
| `ImageMagick` | SUSE:Linux Enterprise Module for Development Tools 15 SP2 | All versions | 7.0.7.34-10.18.1 |
| `ImageMagick` | SUSE:Linux Enterprise Module for Development Tools 15 SP3 | All versions | 7.0.7.34-10.18.1 |
| `ImageMagick` | openSUSE:Leap 15.2 | All versions | 7.0.7.34-lp152.12.18.1 |
| `ImageMagick` | openSUSE:Leap 15.3 | All versions | 7.0.7.34-10.18.1 |

Products: Debian Debian Linux, Imagemagick Imagemagick.

## How do I fix CVE-2021-20176?

Apply the vendor's patch.

## Is CVE-2021-20176 being exploited?

There is no known exploitation of CVE-2021-20176 in the wild and no public exploit code.

## 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-2021-20176 and fix it if it is affected.

What it is: CVE-2021-20176 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 5 Feb 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-2021-20176 in the wild and no public exploit code.

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-2021-20176/ (Markdown: https://insights.sbomify.com/CVE-2021-20176/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20176
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20176
- OSV: https://osv.dev/vulnerability/CVE-2021-20176

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20176/
Summaries are generated and may contain mistakes; the official description above is the record.