# CVE-2020-6807: Use after free in Firefox

> A use-after-free vulnerability in Firefox and Thunderbird allows attackers to cause a crash or potentially execute arbitrary code via stream destruction race conditions.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Mar 2020
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-6807, GHSA-v7mh-jh5r-f65h, UBUNTU-CVE-2020-6807

## What is CVE-2020-6807?

CVE-2020-6807 is a high-severity use after free vulnerability in Canonical Ubuntu Linux, published on 25 Mar 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

When a device was changed while a stream was about to be destroyed, the <code>stream-reinit</code> task may have been executed after the stream was destroyed, causing a use-after-free and a potentially exploitable crash. This vulnerability affects Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2020-6807?

It affects 4 products.


Products: Canonical Ubuntu Linux, Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird.

## How do I fix CVE-2020-6807?

Upgrade to a fixed version.

## Is CVE-2020-6807 being exploited?

There is no known exploitation of CVE-2020-6807 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-2020-6807 and fix it if it is affected.

What it is: CVE-2020-6807 is a high-severity use after free vulnerability in Canonical Ubuntu Linux, published on 25 Mar 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-6807 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-2020-6807/ (Markdown: https://insights.sbomify.com/CVE-2020-6807/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-6807
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-6807
- OSV: https://osv.dev/vulnerability/CVE-2020-6807

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-6807/
Summaries are generated and may contain mistakes; the official description above is the record.