# CVE-2021-3697: Memory corruption in grub2

> A crafted JPEG image can cause heap underflow in GRUB2, potentially allowing code execution or secure boot circumvention.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/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:** 6 Jul 2022
- **Updated:** 3 Aug 2024
- **Also known as:** ALPINE-CVE-2021-3697, AZL-31036, AZL-34785, DEBIAN-CVE-2021-3697, GHSA-pr45-j47f-755r, UBUNTU-CVE-2021-3697

## What is CVE-2021-3697?

CVE-2021-3697 is a high-severity memory corruption vulnerability in Redhat Enterprise Linux, 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 JPEG image may lead the JPEG reader to underflow its data pointer, allowing user-controlled data to be written in heap. To a successful to be performed the attacker needs to perform some triage over the heap layout and craft an image with a malicious format and payload. This vulnerability can lead to data corruption and eventual code execution or secure boot circumvention. This flaw affects grub2 versions prior grub-2.12.

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

## Which versions are affected by CVE-2021-3697?

It affects 12 products.


Products: Gnu Grub2, 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-2021-3697?

Upgrade to a fixed version.

## Is CVE-2021-3697 being exploited?

There is no known exploitation of CVE-2021-3697 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2024-56737](https://insights.sbomify.com/CVE-2024-56737/): Memory corruption in GRUB2 (high 8.8)
- [CVE-2022-28733](https://insights.sbomify.com/CVE-2022-28733/): Integer underflow in grub_net_recv_ip4_packets (high 8.1)
- [CVE-2022-28734](https://insights.sbomify.com/CVE-2022-28734/): Out-of-bounds write when handling split HTTP headers (high 8.1)
- [CVE-2025-61662](https://insights.sbomify.com/CVE-2025-61662/): Grub2: missing unregister call for gettext command may lead to use-after-free (high 7.8)
- [CVE-2024-45782](https://insights.sbomify.com/CVE-2024-45782/): Grub2: fs/hfs: strcpy() using the volume name (fs/hfs.c:382) (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3697 and fix it if it is affected.

What it is: CVE-2021-3697 is a high-severity memory corruption vulnerability in Redhat Enterprise Linux, 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-2021-3697 in the wild and no public exploit code.

Affected product: Redhat Enterprise 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-2021-3697/ (Markdown: https://insights.sbomify.com/CVE-2021-3697/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3697
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3697
- OSV: https://osv.dev/vulnerability/CVE-2021-3697

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3697/
Summaries are generated and may contain mistakes; the official description above is the record.