# CVE-2021-3695: Memory corruption in grub2

> A crafted PNG image triggers a heap out-of-bounds write in GRUB, potentially allowing arbitrary code execution and secure boot bypass.

- **Severity:** Medium 4.5 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L`)
- **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:** 6 Jul 2022
- **Updated:** 3 Aug 2024
- **Also known as:** AZL-31034, AZL-34783, DEBIAN-CVE-2021-3695, GHSA-xjhh-w3rj-8mxm, UBUNTU-CVE-2021-3695

## What is CVE-2021-3695?

CVE-2021-3695 is a medium-severity memory corruption vulnerability in Fedoraproject Fedora, published on 6 Jul 2022. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A crafted 16-bit grayscale PNG image may lead to a out-of-bounds write in the heap area. An attacker may take advantage of that to cause heap data corruption or eventually arbitrary code execution and circumvent secure boot protections. This issue has a high complexity to be exploited as an attacker needs to perform some triage over the heap layout to achieve signifcant results, also the values written into the memory are repeated three times in a row making difficult to produce valid payloads. This flaw affects grub2 versions prior grub-2.12.

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

## Which versions are affected by CVE-2021-3695?

It affects 14 products.


Products: Fedoraproject Fedora, Gnu Grub2, Netapp Ontap Select Deploy Administration Utility, Redhat Codeready Linux Builder, Redhat Developer Tools, Redhat Enterprise Linux, Redhat Enterprise Linux Eus, Redhat Enterprise Linux for Power Little Endian, Redhat Enterprise Linux for Power Little Endian Eus, Redhat Enterprise Linux Server Aus, Redhat Enterprise Linux Server for Power Little Endian Update Services for Sap Solutions, Redhat Enterprise Linux Server Tus, Redhat Openshift, Redhat Openshift Container Platform.

## How do I fix CVE-2021-3695?

Upgrade to a fixed version.

## Is CVE-2021-3695 being exploited?

There is no known exploitation of CVE-2021-3695 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-2021-3695 and fix it if it is affected.

What it is: CVE-2021-3695 is a medium-severity memory corruption vulnerability in Fedoraproject Fedora, published on 6 Jul 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-2021-3695 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-2021-3695/ (Markdown: https://insights.sbomify.com/CVE-2021-3695/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3695
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3695
- OSV: https://osv.dev/vulnerability/CVE-2021-3695

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3695/
Summaries are generated and may contain mistakes; the official description above is the record.