# CVE-2020-15706: Use after free in grub2 in Ubuntu

> A race condition in GRUB2 allows arbitrary code execution and secure boot bypass by redefining a function during execution.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:L/AC:H/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:** 29 Jul 2020
- **Updated:** 16 Sep 2024
- **Also known as:** ALPINE-CVE-2020-15706, DEBIAN-CVE-2020-15706, GHSA-gmqm-wgp3-r69q, UBUNTU-CVE-2020-15706

## What is CVE-2020-15706?

CVE-2020-15706 is a medium-severity use after free vulnerability in Canonical Ubuntu Linux, published on 29 Jul 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

GRUB2 contains a race condition in grub_script_function_create() leading to a use-after-free vulnerability which can be triggered by redefining a function whilst the same function is already executing, leading to arbitrary code execution and secure boot restriction bypass. This issue affects GRUB2 version 2.04 and prior versions.

Weakness: CWE-416 (Use After Free), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2020-15706?

It affects 14 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Gnu Grub2, Microsoft Windows 10, Microsoft Windows 8.1, Microsoft Windows Rt 8.1, Microsoft Windows Server 2012, Microsoft Windows Server 2016, Microsoft Windows Server 2019, Opensuse Leap, Redhat Enterprise Linux, Redhat Enterprise Linux Atomic Host, Redhat Openshift Container Platform, Suse Suse Linux Enterprise Server.

## How do I fix CVE-2020-15706?

Apply the vendor's patch.

## Is CVE-2020-15706 being exploited?

There is no known exploitation of CVE-2020-15706 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-15706 and fix it if it is affected.

What it is: CVE-2020-15706 is a medium-severity use after free vulnerability in Canonical Ubuntu Linux, published on 29 Jul 2020. 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-2020-15706 in the wild and no public exploit code.

Affected product: Canonical Ubuntu 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-2020-15706/ (Markdown: https://insights.sbomify.com/CVE-2020-15706/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15706
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15706
- OSV: https://osv.dev/vulnerability/CVE-2020-15706

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-15706/
Summaries are generated and may contain mistakes; the official description above is the record.