# CVE-2025-6425: The WebCompat WebExtension shipped with Firefox exposed a persistent UUID

> Attackers could obtain a persistent browser-identifying UUID by enumerating WebCompat extension resources, compromising user privacy across browsing modes.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/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:** 24 Jun 2025
- **Updated:** 13 Apr 2026
- **Also known as:** DEBIAN-CVE-2025-6425, GHSA-2h3c-qrcw-962q, UBUNTU-CVE-2025-6425

## What is CVE-2025-6425?

CVE-2025-6425 is a medium-severity vulnerability in Mozilla Firefox, published on 24 Jun 2025. 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

An attacker who enumerated resources from the WebCompat extension could have obtained a persistent UUID that identified the browser, and persisted between containers and normal/private browsing mode, but not profiles. This vulnerability was fixed in Firefox 140, Firefox ESR 115.25, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2025-6425?

It affects 1 product.


Products: Mozilla Firefox.

## How do I fix CVE-2025-6425?

Upgrade to a fixed version.

## Is CVE-2025-6425 being exploited?

There is no known exploitation of CVE-2025-6425 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-2025-6425 and fix it if it is affected.

What it is: CVE-2025-6425 is a medium-severity vulnerability in Mozilla Firefox, published on 24 Jun 2025. 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-2025-6425 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-2025-6425/ (Markdown: https://insights.sbomify.com/CVE-2025-6425/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-6425
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-6425
- OSV: https://osv.dev/vulnerability/CVE-2025-6425

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-6425/
Summaries are generated and may contain mistakes; the official description above is the record.