# CVE-2021-28652: Denial of service in n/a

> A trusted client can trigger memory leaks in Squid's Cache Manager API, leading to a Denial of Service condition.

- **Severity:** Medium 4.9 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 May 2021
- **Updated:** 3 Aug 2024
- **Also known as:** ALPINE-CVE-2021-28652, DEBIAN-CVE-2021-28652, GHSA-m47m-9hvw-7447, UBUNTU-CVE-2021-28652

## What is CVE-2021-28652?

CVE-2021-28652 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 27 May 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to incorrect parser validation, it allows a Denial of Service attack against the Cache Manager API. This allows a trusted client to trigger memory leaks that. over time, lead to a Denial of Service via an unspecified short query string. This attack is limited to clients with Cache Manager API access privilege.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2021-28652?

It affects 3 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Squid-Cache Squid.

## How do I fix CVE-2021-28652?

Upgrade to a fixed version.

## Is CVE-2021-28652 being exploited?

There is no known exploitation of CVE-2021-28652 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28652 and fix it if it is affected.

What it is: CVE-2021-28652 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 27 May 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-28652 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-28652/ (Markdown: https://insights.sbomify.com/CVE-2021-28652/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28652
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28652
- OSV: https://osv.dev/vulnerability/CVE-2021-28652

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28652/
Summaries are generated and may contain mistakes; the official description above is the record.