# CVE-2023-4049: Use after free in Firefox

> Race conditions in reference counting could lead to exploitable use-after-free vulnerabilities in Firefox, allowing potential code execution.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/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:** 1 Aug 2023
- **Updated:** 13 Feb 2025
- **Also known as:** DEBIAN-CVE-2023-4049, GHSA-6jfh-jrm6-9hm8, UBUNTU-CVE-2023-4049

## What is CVE-2023-4049?

CVE-2023-4049 is a medium-severity use after free vulnerability in Debian Debian Linux, published on 1 Aug 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Race conditions in reference counting code were found through code inspection. These could have resulted in potentially exploitable use-after-free vulnerabilities. This vulnerability affects Firefox < 116, Firefox ESR < 102.14, and Firefox ESR < 115.1.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2023-4049?

It affects 2 products.


Products: Debian Debian Linux, Mozilla Firefox.

## How do I fix CVE-2023-4049?

Upgrade to a fixed version.

## Is CVE-2023-4049 being exploited?

There is no known exploitation of CVE-2023-4049 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-4049 and fix it if it is affected.

What it is: CVE-2023-4049 is a medium-severity use after free vulnerability in Debian Debian Linux, published on 1 Aug 2023. 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-2023-4049 in the wild and no public exploit code.

Affected product: Debian Debian 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-2023-4049/ (Markdown: https://insights.sbomify.com/CVE-2023-4049/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-4049
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-4049
- OSV: https://osv.dev/vulnerability/CVE-2023-4049

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-4049/
Summaries are generated and may contain mistakes; the official description above is the record.