# CVE-2021-3466: Memory corruption in libmicrohttpd

> A buffer overflow in libmicrohttpd allows remote attackers to write arbitrary data, potentially compromising confidentiality, integrity, and availability.

- **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:** Yes
- **Published:** 25 Mar 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-3466, ECHO-7632-c491-0f24, GHSA-vjm5-89cg-7hj8

## What is CVE-2021-3466?

CVE-2021-3466 is a critical memory corruption vulnerability in Fedoraproject Fedora, published on 25 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in libmicrohttpd. A missing bounds check in the post_process_urlencoded function leads to a buffer overflow, allowing a remote attacker to write arbitrary data in an application that uses libmicrohttpd. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability. Only version 0.9.70 is vulnerable.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2021-3466?

It affects 3 products.


Products: Fedoraproject Fedora, Gnu Libmicrohttpd, Redhat Enterprise Linux.

## How do I fix CVE-2021-3466?

Upgrade to a fixed version.

## Is CVE-2021-3466 being exploited?

There is no known exploitation of CVE-2021-3466 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-2021-3466 and fix it if it is affected.

What it is: CVE-2021-3466 is a critical memory corruption vulnerability in Fedoraproject Fedora, published on 25 Mar 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-2021-3466 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-2021-3466/ (Markdown: https://insights.sbomify.com/CVE-2021-3466/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3466
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3466
- OSV: https://osv.dev/vulnerability/CVE-2021-3466

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3466/
Summaries are generated and may contain mistakes; the official description above is the record.