# CVE-2018-18500: Use after free in n/a

> A use-after-free flaw in HTML5 stream parsing allows attackers to cause crashes or potentially execute arbitrary code in Firefox and Thunderbird.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 5 Feb 2019
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2018-18500, GHSA-6hxm-h9g7-cg3m, UBUNTU-CVE-2018-18500

## What is CVE-2018-18500?

CVE-2018-18500 is a critical use after free vulnerability in Canonical Ubuntu Linux, published on 5 Feb 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A use-after-free vulnerability can occur while parsing an HTML5 stream in concert with custom HTML elements. This results in the stream parser object being freed while still in use, leading to a potentially exploitable crash. This vulnerability affects Thunderbird < 60.5, Firefox ESR < 60.5, and Firefox < 65.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2018-18500?

It affects 11 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Server, Redhat Enterprise Linux Server Aus, Redhat Enterprise Linux Server Eus, Redhat Enterprise Linux Server Tus, Redhat Enterprise Linux Workstation.

## How do I fix CVE-2018-18500?

Upgrade to a fixed version.

## Is CVE-2018-18500 being exploited?

There is no known exploitation of CVE-2018-18500 in the wild and no public exploit code.

Public exploit code:

- PoC for CVE-2018-18500 - Firefox Use-After-Free (github_poc): https://github.com/sophoslabs/CVE-2018-18500

## 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-2018-18500 and fix it if it is affected.

What it is: CVE-2018-18500 is a critical use after free vulnerability in Canonical Ubuntu Linux, published on 5 Feb 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-18500 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-2018-18500/ (Markdown: https://insights.sbomify.com/CVE-2018-18500/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-18500
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-18500
- OSV: https://osv.dev/vulnerability/CVE-2018-18500

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-18500/
Summaries are generated and may contain mistakes; the official description above is the record.