# CVE-2021-3501: Memory corruption in kernel

> A local attacker can trigger an out-of-bounds write in the Linux kernel KVM API, compromising data integrity and system availability.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/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:** 5 May 2021
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-6569, DEBIAN-CVE-2021-3501, GHSA-hvwc-6fg8-r6p5, RHSA-2021:2165, UBUNTU-CVE-2021-3501

## What is CVE-2021-3501?

CVE-2021-3501 is a high-severity memory corruption vulnerability in Fedoraproject Fedora, published on 5 May 2021. 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 in versions before 5.12. The value of internal.ndata, in the KVM API, is mapped to an array index, which can be updated by a user process at anytime which could lead to an out-of-bounds write. The highest threat from this vulnerability is to data integrity and system availability.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-3501?

It affects 19 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `kpatch-patch-4_18_0-305` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1-1.el8 |
| `kpatch-patch-4_18_0-305-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1-1.el8 |
| `kpatch-patch-4_18_0-305-debugsource` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1-1.el8 |

Products: Fedoraproject Fedora, Linux kernel, Netapp Cloud Backup, Netapp H300e Firmware, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware, Netapp H500e Firmware, Netapp H500s Firmware, Netapp H700e Firmware, Netapp H700s Firmware, Netapp Solidfire Baseboard Management Controller Firmware, Redhat Enterprise Linux, 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 Virtualization, Redhat Virtualization Host.

## How do I fix CVE-2021-3501?

Apply the vendor's patch.

## Is CVE-2021-3501 being exploited?

There is no known exploitation of CVE-2021-3501 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3501 and fix it if it is affected.

What it is: CVE-2021-3501 is a high-severity memory corruption vulnerability in Fedoraproject Fedora, published on 5 May 2021. 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-2021-3501 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. 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-2021-3501/ (Markdown: https://insights.sbomify.com/CVE-2021-3501/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3501
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3501
- OSV: https://osv.dev/vulnerability/CVE-2021-3501

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3501/
Summaries are generated and may contain mistakes; the official description above is the record.