# CVE-2021-3968: Heap-based Buffer Overflow in vim/vim

> A heap-based buffer overflow in Vim allows attackers to execute arbitrary code or cause a denial of service via crafted input.

- **Severity:** High 8.0 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 19 Nov 2021
- **Updated:** 8 Oct 2026
- **Also known as:** ALPINE-CVE-2021-3968, AZL-6945, DEBIAN-CVE-2021-3968, GHSA-p5c5-45cp-hjw4

## What is CVE-2021-3968?

CVE-2021-3968 is a high-severity memory corruption vulnerability in Fedoraproject Fedora, published on 19 Nov 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

vim is vulnerable to Heap-based Buffer Overflow

Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2021-3968?

It affects 2 products.


Products: Fedoraproject Fedora, Vim Vim.

## How do I fix CVE-2021-3968?

Apply the vendor's patch.

## Is CVE-2021-3968 being exploited?

There is no known exploitation of CVE-2021-3968 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3968 and fix it if it is affected.

What it is: CVE-2021-3968 is a high-severity memory corruption vulnerability in Fedoraproject Fedora, published on 19 Nov 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-3968 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. 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-2021-3968/ (Markdown: https://insights.sbomify.com/CVE-2021-3968/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3968
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3968
- OSV: https://osv.dev/vulnerability/CVE-2021-3968

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3968/
Summaries are generated and may contain mistakes; the official description above is the record.