# CVE-2025-5262: Use after free in Thunderbird

> A double-free vulnerability in Thunderbird's WebRTC encoder initialization allows attackers to cause memory corruption, potentially leading to code execution or crashes.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/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:** 27 May 2025
- **Updated:** 25 Aug 2025
- **Also known as:** GHSA-v5j6-fjmw-w724, UBUNTU-CVE-2025-5262

## What is CVE-2025-5262?

CVE-2025-5262 is a high-severity use after free vulnerability in Mozilla Thunderbird, published on 27 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A double-free could have occurred in `vpx_codec_enc_init_multi` after a failed allocation when initializing the encoder for WebRTC. This could have caused memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 139 and Thunderbird < 128.11.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2025-5262?

It affects 1 product.


Products: Mozilla Thunderbird.

## How do I fix CVE-2025-5262?

Upgrade to a fixed version.

## Is CVE-2025-5262 being exploited?

There is no known exploitation of CVE-2025-5262 in the wild and no public exploit code.

## Other vulnerabilities in Mozilla Thunderbird

- [CVE-2026-92238](https://insights.sbomify.com/CVE-2026-92238/): Ambiguous parsing of mail headers (critical 9.8)
- [CVE-2026-84637](https://insights.sbomify.com/CVE-2026-84637/): Calendar invitation attachments could launch local executables (critical 9.8)
- [CVE-2021-43529](https://insights.sbomify.com/CVE-2021-43529/): Memory corruption in Thunderbird (critical 9.8)
- [CVE-2019-11703](https://insights.sbomify.com/CVE-2019-11703/): Memory corruption in Thunderbird (critical 9.8)
- [CVE-2019-11704](https://insights.sbomify.com/CVE-2019-11704/): Memory corruption in Thunderbird (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-5262 and fix it if it is affected.

What it is: CVE-2025-5262 is a high-severity use after free vulnerability in Mozilla Thunderbird, published on 27 May 2025. 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-2025-5262 in the wild and no public exploit code.

Affected product: Mozilla Thunderbird. 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-2025-5262/ (Markdown: https://insights.sbomify.com/CVE-2025-5262/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-5262
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-5262
- OSV: https://osv.dev/vulnerability/CVE-2025-5262

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-5262/
Summaries are generated and may contain mistakes; the official description above is the record.