# CVE-2006-4253: Use after free in n/a

> Remote attackers can cause a crash or execute arbitrary code in Mozilla Firefox via a race condition involving JavaScript timed events and XML loading.

- **Severity:** High 7.6 (`AV:N/AC:H/Au:N/C:C/I:C/A:C`)
- **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:** 21 Aug 2006
- **Updated:** 7 Aug 2024
- **Also known as:** CVE-2006-4261, DEBIAN-CVE-2006-4253, GHSA-42hr-qcx2-4fr6

## What is CVE-2006-4253?

CVE-2006-4253 is a high-severity use after free vulnerability in Mozilla Firefox, published on 21 Aug 2006. 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

Concurrency vulnerability in Mozilla Firefox 1.5.0.6 and earlier allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via multiple Javascript timed events that load a deeply nested XML file, followed by redirecting the browser to another page, which leads to a concurrency failure that causes structures to be freed incorrectly, as demonstrated by (1) ffoxdie and (2) ffoxdie3.  NOTE: it has been reported that Netscape 8.1 and K-Meleon 1.0.1 are also affected by ffoxdie.  Mozilla confirmed to CVE that ffoxdie and ffoxdie3 trigger the same underlying vulnerability.  NOTE: it was later reported that Firefox 2.0 RC2 and 1.5.0.7 are also affected.

Weakness: CWE-264

## Which versions are affected by CVE-2006-4253?

It affects 3 products.


Products: K-Meleon Project K-Meleon, Mozilla Firefox, Netscape Navigator.

## How do I fix CVE-2006-4253?

Upgrade to a fixed version.

## Is CVE-2006-4253 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2006-4253 exists.

Public exploit code:

- Mozilla Firefox 1.0.x - JavaScript Handler Race Condition Memory Corruption (exploitdb)

## Other vulnerabilities in Mozilla Firefox

- [CVE-2006-1942](https://insights.sbomify.com/CVE-2006-1942/): Other in n/a (medium 5.1)
- [CVE-2005-4134](https://insights.sbomify.com/CVE-2005-4134/): Denial of service in n/a (medium 5.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2006-4253 and fix it if it is affected.

What it is: CVE-2006-4253 is a high-severity use after free vulnerability in Mozilla Firefox, published on 21 Aug 2006. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2006-4253 exists.

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-2006-4253/ (Markdown: https://insights.sbomify.com/CVE-2006-4253/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2006-4253
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2006-4253
- OSV: https://osv.dev/vulnerability/CVE-2006-4253

---
From sbomify Insights: https://insights.sbomify.com/CVE-2006-4253/
Summaries are generated and may contain mistakes; the official description above is the record.