# CVE-2026-66039: FFmpeg MACE6 Audio Decoder Heap Out-of-Bounds Write via CAF File

> A signed integer overflow in FFmpeg's MACE6 decoder allows heap corruption and potential code execution via crafted CAF files.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA: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 Jul 2026
- **Updated:** 29 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-66039, ECHO-96cc-ea04-811e, GHSA-84qc-6h9r-4w33, JLSEC-2026-1185, MINI-cg54-5cxx-pfxv, UBUNTU-CVE-2026-66039

## What is CVE-2026-66039?

CVE-2026-66039 is a high-severity vulnerability in Ffmpeg Ffmpeg, published on 24 Jul 2026. 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

FFmpeg through 8.1.2, fixed in commit aafb5c6, contains a signed integer overflow vulnerability in the MACE6 audio decoder that allows attackers to corrupt heap memory by supplying a crafted CAF file with a malicious bytes_per_packet value. Attackers can craft a CAF file with oversized bytes_per_packet and frames_per_packet values in the desc chunk to trigger an integer overflow in mace_decode_frame() during output sample count computation, resulting in an undersized buffer allocation and heap out-of-bounds write that could enable code execution.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-66039?

It affects 1 product.


Products: Ffmpeg Ffmpeg.

## How do I fix CVE-2026-66039?

Apply the vendor's patch.

## Is CVE-2026-66039 being exploited?

There is no known exploitation of CVE-2026-66039 in the wild and no public exploit code.

## Other vulnerabilities in Ffmpeg Ffmpeg

- [CVE-2013-0864](https://insights.sbomify.com/CVE-2013-0864/): Memory corruption in n/a (critical 10.0)
- [CVE-2013-0872](https://insights.sbomify.com/CVE-2013-0872/): Memory corruption in n/a (critical 10.0)
- [CVE-2013-0873](https://insights.sbomify.com/CVE-2013-0873/): Memory corruption in n/a (critical 10.0)
- [CVE-2013-4265](https://insights.sbomify.com/CVE-2013-4265/): Null dereference in n/a (critical 10.0)
- [CVE-2011-3937](https://insights.sbomify.com/CVE-2011-3937/): Memory corruption in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66039 and fix it if it is affected.

What it is: CVE-2026-66039 is a high-severity vulnerability in Ffmpeg Ffmpeg, published on 24 Jul 2026. 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-2026-66039 in the wild and no public exploit code.

Affected product: Ffmpeg Ffmpeg. 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-2026-66039/ (Markdown: https://insights.sbomify.com/CVE-2026-66039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66039
- OSV: https://osv.dev/vulnerability/CVE-2026-66039

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66039/
Summaries are generated and may contain mistakes; the official description above is the record.