# CVE-2021-40166: Use after free in Revit, Inventor, Infraworks, Navisworks, Fusion, Infrastructure Parts Editors, Autodesk Advanced Steel, Civil 3D, AutoCAD, AutoCAD LT, AutoCAD Architecture, AutoCAD Electrical, AutoCAD Map 3D, AutoCAD Mechanical, AutoCAD MEP, AutoCAD Plant 3D

> Attackers can execute arbitrary code by tricking users into opening a maliciously crafted PNG file in Autodesk CAD applications.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/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:** No
- **Published:** 7 Oct 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-mfx9-gcm4-c79c

## What is CVE-2021-40166?

CVE-2021-40166 is a high-severity use after free vulnerability in Autodesk Autocad, published on 7 Oct 2022. 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 maliciously crafted PNG file in Autodesk Image Processing component may be used to attempt to free an object that has already been freed while parsing them. This vulnerability may be exploited by attackers to execute arbitrary code.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-40166?

It affects 19 products.


Products: Autodesk Autocad, Autodesk Autocad Advance Steel, Autodesk Autocad Architecture, Autodesk Autocad Civil 3d, Autodesk Autocad Electrical, Autodesk Autocad Lt, Autodesk Autocad Map 3d, Autodesk Autocad Mechanical, Autodesk Autocad Mep, Autodesk Autocad Plant 3d, Autodesk Design Review, Autodesk Dwg Trueview, Autodesk Fusion, Autodesk Infrastructure Parts Editor, Autodesk Infraworks, Autodesk Inventor, Autodesk Navisworks, Autodesk Revit, Autodesk Storm and Sanitary Analysis.

## How do I fix CVE-2021-40166?

No fix has been published for CVE-2021-40166 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40166 being exploited?

There is no known exploitation of CVE-2021-40166 in the wild and no public exploit code.

## Other vulnerabilities in Autodesk Autocad

- [CVE-2023-29073](https://insights.sbomify.com/CVE-2023-29073/): Memory corruption in AutoCAD, Advance Steel and Civil 3D (critical 9.8)
- [CVE-2023-29074](https://insights.sbomify.com/CVE-2023-29074/): Memory corruption in AutoCAD, Advance Steel and Civil 3D (critical 9.8)
- [CVE-2023-29075](https://insights.sbomify.com/CVE-2023-29075/): Memory corruption in AutoCAD, Advance Steel and Civil 3D (critical 9.8)
- [CVE-2023-29076](https://insights.sbomify.com/CVE-2023-29076/): Memory corruption in AutoCAD, Advance Steel and Civil 3D (critical 9.8)
- [CVE-2024-7991](https://insights.sbomify.com/CVE-2024-7991/): Autodesk AutoCAD DWG Out-of-Bounds Write Code Execution Vulnerability (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40166 and fix it if it is affected.

What it is: CVE-2021-40166 is a high-severity use after free vulnerability in Autodesk Autocad, published on 7 Oct 2022. 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-2021-40166 in the wild and no public exploit code.

Affected product: Autodesk Autocad. 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-2021-40166/ (Markdown: https://insights.sbomify.com/CVE-2021-40166/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40166
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40166
- OSV: https://osv.dev/vulnerability/CVE-2021-40166

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40166/
Summaries are generated and may contain mistakes; the official description above is the record.