# CVE-2020-27749: Memory corruption in grub2

> Attacker can overflow stack buffer in GRUB2 to execute code and bypass Secure Boot, compromising system integrity and availability.

- **Severity:** Medium 6.7 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Mar 2021
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2020-27749, AZL-6463, DEBIAN-CVE-2020-27749, GHSA-258p-xh3c-g68w, UBUNTU-CVE-2020-27749

## What is CVE-2020-27749?

CVE-2020-27749 is a medium-severity memory corruption vulnerability in Fedoraproject Fedora, published on 3 Mar 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 grub2 in versions prior to 2.06. Variable names present are expanded in the supplied command line into their corresponding variable contents, using a 1kB stack buffer for temporary storage, without sufficient bounds checking. If the function is called with a command line that references a variable with a sufficiently large payload, it is possible to overflow the stack buffer, corrupt the stack frame and control execution which could also circumvent Secure Boot protections. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

Weakness: CWE-787 (Out-of-bounds Write), CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2020-27749?

It affects 8 products.


Products: Fedoraproject Fedora, Gnu Grub2, Netapp Ontap Select Deploy Administration Utility, Redhat Enterprise Linux, Redhat Enterprise Linux Server Aus, Redhat Enterprise Linux Server Eus, Redhat Enterprise Linux Server Tus, Redhat Enterprise Linux Workstation.

## How do I fix CVE-2020-27749?

Upgrade to a fixed version.

## Is CVE-2020-27749 being exploited?

There is no known exploitation of CVE-2020-27749 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-2020-27749 and fix it if it is affected.

What it is: CVE-2020-27749 is a medium-severity memory corruption vulnerability in Fedoraproject Fedora, published on 3 Mar 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-2020-27749 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-2020-27749/ (Markdown: https://insights.sbomify.com/CVE-2020-27749/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27749
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27749
- OSV: https://osv.dev/vulnerability/CVE-2020-27749

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-27749/
Summaries are generated and may contain mistakes; the official description above is the record.