# CVE-2018-12396: Security feature bypass in Firefox

> A WebExtension can execute content scripts in disallowed contexts, enabling privilege escalation on restricted sites in Firefox.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N`)
- **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:** 28 Feb 2019
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2018-12396, GHSA-5c59-7337-gvv9, UBUNTU-CVE-2018-12396

## What is CVE-2018-12396?

CVE-2018-12396 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 28 Feb 2019. 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

A vulnerability where a WebExtension can run content scripts in disallowed contexts following navigation or other events. This allows for potential privilege escalation by the WebExtension on sites where content scripts should not be run. This vulnerability affects Firefox ESR < 60.3 and Firefox < 63.

Weakness: CWE-732 (Incorrect Permission Assignment for Critical Resource)

## Which versions are affected by CVE-2018-12396?

It affects 10 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Mozilla Firefox, Mozilla Firefox Esr, 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-2018-12396?

Upgrade to a fixed version.

## Is CVE-2018-12396 being exploited?

There is no known exploitation of CVE-2018-12396 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-2018-12396 and fix it if it is affected.

What it is: CVE-2018-12396 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 28 Feb 2019. 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-2018-12396 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-2018-12396/ (Markdown: https://insights.sbomify.com/CVE-2018-12396/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-12396
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-12396
- OSV: https://osv.dev/vulnerability/CVE-2018-12396

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-12396/
Summaries are generated and may contain mistakes; the official description above is the record.