# CVE-2021-40531: Security feature bypass in n/a

> Sketch allows bypassing macOS file quarantine via library feeds, enabling remote code execution when files are automatically opened.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-jf84-45wf-mjgm

## What is CVE-2021-40531?

CVE-2021-40531 is a critical vulnerability in n/a, published on 6 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Sketch before 75 allows library feeds to be used to bypass file quarantine. Files are automatically downloaded and opened, without the com.apple.quarantine extended attribute. This results in remote code execution, as demonstrated by CommandString in a terminal profile to Terminal.app.

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type)

## Which versions are affected by CVE-2021-40531?

It affects 1 product.


Products: Sketch Sketch.

## How do I fix CVE-2021-40531?

No fix has been published for CVE-2021-40531 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40531 being exploited?

There is no known exploitation of CVE-2021-40531 in the wild and no public exploit code.

Public exploit code:

- Quarantine bypass and RCE vulnerability in Sketch (proof-of-concept) (github_poc): https://github.com/jonpalmisc/CVE-2021-40531

## Other vulnerabilities in n/a

- [CVE-2002-2047](https://insights.sbomify.com/CVE-2002-2047/): Command injection in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40531 and fix it if it is affected.

What it is: CVE-2021-40531 is a critical vulnerability in n/a, published on 6 Sep 2021. 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-2021-40531 in the wild and no public exploit code.

Affected product: n/a. 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-2021-40531/ (Markdown: https://insights.sbomify.com/CVE-2021-40531/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40531
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40531
- OSV: https://osv.dev/vulnerability/CVE-2021-40531

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40531/
Summaries are generated and may contain mistakes; the official description above is the record.