# CVE-2021-4166: Out-of-bounds Read in vim/vim


- **Severity:** High 7.1 (`CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 25 Dec 2021
- **Updated:** 8 Oct 2026
- **Also known as:** ALPINE-CVE-2021-4166, AZL-7075, DEBIAN-CVE-2021-4166, GHSA-5q95-22v3-59qw, UBUNTU-CVE-2021-4166

## What is CVE-2021-4166?

CVE-2021-4166 is a high-severity vulnerability in Apple Mac Os X, published on 25 Dec 2021. 

### Official description

vim is vulnerable to Out-of-bounds Read

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2021-4166?

It affects 8 products.


Products: Apple Mac Os X, Apple Macos, Debian Debian Linux, Fedoraproject Fedora, Opensuse Factory, Redhat Enterprise Linux, Suse Linux Enterprise, Vim Vim.

## How do I fix CVE-2021-4166?

Upgrade to a fixed version.

## Is CVE-2021-4166 being exploited?

There is no known exploitation of CVE-2021-4166 in the wild and no public exploit code.

## Other vulnerabilities in Apple Mac Os X

- [CVE-2014-7169](https://insights.sbomify.com/CVE-2014-7169/): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution (critical 9.8, exploited in the wild)
- [CVE-2014-6271](https://insights.sbomify.com/CVE-2014-6271/): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution (critical 9.8, exploited in the wild)
- [CVE-2012-1823](https://insights.sbomify.com/CVE-2012-1823/): PHP-CGI Query String Parameter (critical 9.8, exploited in the wild)
- [CVE-2021-30713](https://insights.sbomify.com/CVE-2021-30713/): Apple macOS Unspecified (high 7.8, exploited in the wild)
- [CVE-2019-8526](https://insights.sbomify.com/CVE-2019-8526/): Apple macOS Use-After-Free (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4166 and fix it if it is affected.

What it is: CVE-2021-4166 is a high-severity vulnerability in Apple Mac Os X, published on 25 Dec 2021. 
Exploitation: There is no known exploitation of CVE-2021-4166 in the wild and no public exploit code.

Affected product: Apple Mac Os X. 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-2021-4166/ (Markdown: https://insights.sbomify.com/CVE-2021-4166/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4166
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4166
- OSV: https://osv.dev/vulnerability/CVE-2021-4166

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4166/
Summaries are generated and may contain mistakes; the official description above is the record.