# CVE-2021-3669: Denial of service in kernel

> A flaw in the Linux kernel allows resource exhaustion and denial of service due to inefficient shared memory usage scaling.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Aug 2022
- **Updated:** 3 Nov 2025
- **Also known as:** AZL-10676, AZL-34859, DEBIAN-CVE-2021-3669, GHSA-fr2g-fcjj-v8hc, UBUNTU-CVE-2021-3669

## What is CVE-2021-3669?

CVE-2021-3669 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 26 Aug 2022. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in the Linux kernel. Measuring usage of the shared memory does not scale with large shared memory segment counts which could lead to resource exhaustion and DoS.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2021-3669?

It affects 23 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Ibm Spectrum Copy Data Management, Ibm Spectrum Protect Plus, Linux kernel, Redhat Build of Quarkus, Redhat Codeready Linux Builder, Redhat Developer Tools, Redhat Enterprise Linux, Redhat Enterprise Linux Aus, Redhat Enterprise Linux for Ibm Z Systems, Redhat Enterprise Linux for Ibm Z Systems Eus, Redhat Enterprise Linux for Power Little Endian, Redhat Enterprise Linux for Power Little Endian Eus, Redhat Enterprise Linux for Real Time, Redhat Enterprise Linux for Real Time for Nfv, Redhat Enterprise Linux for Real Time for Nfv Tus, Redhat Enterprise Linux for Real Time Tus, Redhat Enterprise Linux Server Aus, Redhat Enterprise Linux Server for Power Little Endian Update Services for Sap Solutions and 3 more.

## How do I fix CVE-2021-3669?

Apply the vendor's patch.

## Is CVE-2021-3669 being exploited?

There is no known exploitation of CVE-2021-3669 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-2021-3669 and fix it if it is affected.

What it is: CVE-2021-3669 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 26 Aug 2022. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3669 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-2021-3669/ (Markdown: https://insights.sbomify.com/CVE-2021-3669/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3669
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3669
- OSV: https://osv.dev/vulnerability/CVE-2021-3669

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3669/
Summaries are generated and may contain mistakes; the official description above is the record.