# CVE-2021-4037: Kernel: security regression for cve-2018-13405

> Local attackers can create XFS files with unintended group ownership and SGID bits, leading to excessive permissions and potential privilege escalation.

- **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:** 24 Aug 2022
- **Updated:** 14 Oct 2026
- **Also known as:** DEBIAN-CVE-2021-4037, GHSA-gvgr-4fph-m6hc, UBUNTU-CVE-2021-4037

## What is CVE-2021-4037?

CVE-2021-4037 is a medium-severity vulnerability in Debian Debian Linux, published on 24 Aug 2022. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability was found in the fs/inode.c:inode_init_owner() function logic of the LInux kernel that allows local users to create files for the XFS file-system with an unintended group ownership and with group execution and SGID permission bits set, in a scenario where a directory is SGID and belongs to a certain group and is writable by a user who is not a member of this group. This can lead to excessive permissions granted in case when they should not.  This vulnerability is similar to the previous CVE-2018-13405 and adds the missed fix for the XFS.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2021-4037?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2021-4037?

Apply the vendor's patch.

## Is CVE-2021-4037 being exploited?

There is no known exploitation of CVE-2021-4037 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-2021-4037 and fix it if it is affected.

What it is: CVE-2021-4037 is a medium-severity vulnerability in Debian Debian Linux, published on 24 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-2021-4037 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-2021-4037/ (Markdown: https://insights.sbomify.com/CVE-2021-4037/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4037
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4037
- OSV: https://osv.dev/vulnerability/CVE-2021-4037

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4037/
Summaries are generated and may contain mistakes; the official description above is the record.