# CVE-2026-16394: Mitigation bypass in the DOM: Security component

> Attackers can bypass DOM security mitigations in Firefox and Thunderbird, potentially enabling further exploitation of the browser environment.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Jul 2026
- **Updated:** 22 Jul 2026
- **Also known as:** GHSA-qvxh-vvjm-vpwg, UBUNTU-CVE-2026-16394

## What is CVE-2026-16394?

CVE-2026-16394 is a critical vulnerability in Mozilla Firefox, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

Weakness: CWE-693 (Protection Mechanism Failure)

## Which versions are affected by CVE-2026-16394?

It affects 1 product.


Products: Mozilla Firefox.

## How do I fix CVE-2026-16394?

Upgrade to a fixed version.

## Is CVE-2026-16394 being exploited?

There is no known exploitation of CVE-2026-16394 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla Firefox

- [CVE-2019-11708](https://insights.sbomify.com/CVE-2019-11708/): Mozilla Firefox and Thunderbird Sandbox Escape (critical 10.0, exploited in the wild)
- [CVE-2010-3765](https://insights.sbomify.com/CVE-2010-3765/): Mozilla Multiple Products Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2022-26486](https://insights.sbomify.com/CVE-2022-26486/): Mozilla Firefox Use-After-Free (critical 9.6, exploited in the wild)
- [CVE-2022-26485](https://insights.sbomify.com/CVE-2022-26485/): Mozilla Firefox Use-After-Free (high 8.8, exploited in the wild)
- [CVE-2019-11707](https://insights.sbomify.com/CVE-2019-11707/): Mozilla Firefox and Thunderbird Type Confusion (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-16394 and fix it if it is affected.

What it is: CVE-2026-16394 is a critical vulnerability in Mozilla Firefox, published on 21 Jul 2026. 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-2026-16394 in the wild and no public exploit code.

Affected product: Mozilla Firefox. 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-2026-16394/ (Markdown: https://insights.sbomify.com/CVE-2026-16394/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-16394
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16394
- OSV: https://osv.dev/vulnerability/CVE-2026-16394

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-16394/
Summaries are generated and may contain mistakes; the official description above is the record.