# CVE-2021-20216: Denial of service in privoxy

> A memory leak in Privoxy during failed decompression allows attackers to cause a denial of service by exhausting system resources.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** ALPINE-CVE-2021-20216, DEBIAN-CVE-2021-20216, GHSA-3429-2hmm-5vvx, UBUNTU-CVE-2021-20216

## What is CVE-2021-20216?

CVE-2021-20216 is a high-severity denial of service vulnerability in privoxy, 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 Privoxy in versions before 3.0.31. A memory leak that occurs when decompression fails unexpectedly may lead to a denial of service. The highest threat from this vulnerability is to system availability.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2021-20216?

It affects 1 product.


Products: Privoxy Privoxy.

## How do I fix CVE-2021-20216?

Upgrade to a fixed version.

## Is CVE-2021-20216 being exploited?

There is no known exploitation of CVE-2021-20216 in the wild and no public exploit code.

## Other vulnerabilities in privoxy

- [CVE-2019-3699](https://insights.sbomify.com/CVE-2019-3699/): Local privilege escalation from user privoxy to root (high 7.7)
- [CVE-2021-44540](https://insights.sbomify.com/CVE-2021-44540/): Denial of service in Privoxy (high 7.5)
- [CVE-2021-44541](https://insights.sbomify.com/CVE-2021-44541/): Denial of service in Privoxy (high 7.5)
- [CVE-2021-44542](https://insights.sbomify.com/CVE-2021-44542/): Denial of service in Privoxy (high 7.5)
- [CVE-2021-20209](https://insights.sbomify.com/CVE-2021-20209/): Denial of service in privoxy (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20216 and fix it if it is affected.

What it is: CVE-2021-20216 is a high-severity denial of service vulnerability in privoxy, 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-2021-20216 in the wild and no public exploit code.

Affected product: privoxy. 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-2021-20216/ (Markdown: https://insights.sbomify.com/CVE-2021-20216/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20216
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20216
- OSV: https://osv.dev/vulnerability/CVE-2021-20216

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20216/
Summaries are generated and may contain mistakes; the official description above is the record.