# CVE-2021-4002: Information disclosure in kernel

> A local attacker can exploit a memory leak in hugetlbfs to gain unauthorized access to sensitive data.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N`)
- **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:** 3 Mar 2022
- **Updated:** 3 Aug 2024
- **Also known as:** AZL-8995, DEBIAN-CVE-2021-4002, GHSA-7jmv-5cqq-75jg, UBUNTU-CVE-2021-4002, USN-5206-1, USN-5211-1

## What is CVE-2021-4002?

CVE-2021-4002 is a medium-severity vulnerability in Debian Debian Linux, published on 3 Mar 2022. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A memory leak flaw in the Linux kernel's hugetlbfs memory usage was found in the way the user maps some regions of memory twice using shmget() which are aligned to PUD alignment with the fault of some of the memory pages. A local user could use this flaw to get unauthorized access to some data.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime), CWE-459 (Incomplete Cleanup)

## Which versions are affected by CVE-2021-4002?

It affects 6 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Linux kernel, Oracle Communications Cloud Native Core Binding Support Function, Oracle Communications Cloud Native Core Network Exposure Function, Oracle Communications Cloud Native Core Policy.

## How do I fix CVE-2021-4002?

Apply the vendor's patch.

## Is CVE-2021-4002 being exploited?

There is no known exploitation of CVE-2021-4002 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-2021-4002 and fix it if it is affected.

What it is: CVE-2021-4002 is a medium-severity vulnerability in Debian Debian Linux, published on 3 Mar 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-2021-4002 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-2021-4002/ (Markdown: https://insights.sbomify.com/CVE-2021-4002/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4002
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4002
- OSV: https://osv.dev/vulnerability/CVE-2021-4002

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4002/
Summaries are generated and may contain mistakes; the official description above is the record.