# CVE-2026-70631: FFmpeg 0.5 < 9.0 Uninitialized Heap Memory Read in TIFF Decoder

> Attackers can expose sensitive heap memory data by crafting TIFF files that trigger uninitialized memory reads in FFmpeg's TIFF decoder.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 Aug 2026
- **Updated:** 14 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-70631, ECHO-fb13-cd27-af33, GHSA-5f73-3r3j-p8mr, JLSEC-2026-1191, UBUNTU-CVE-2026-70631

## What is CVE-2026-70631?

CVE-2026-70631 is a medium-severity vulnerability in Ffmpeg Ffmpeg, published on 6 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

FFmpeg versions from 0.5 up to, but not including, 9.0 contain an uninitialized heap memory disclosure vulnerability in the native TIFF decoder in libavcodec/tiff.c. An attacker who can cause FFmpeg to decode a crafted TIFF file can supply a valid Deflate-compressed strip that terminates successfully after producing fewer bytes than the declared strip requires. The tiff_unpack_zlib() function allocates a heap buffer sized for the full declared strip but copies all declared rows via memcpy() regardless of how many bytes zlib actually decompressed, causing unwritten bytes that can contain stale data from prior heap allocations to be incorporated into decoded image output and potentially exposing sensitive data in persistent services.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2026-70631?

It affects 1 product.


Products: Ffmpeg Ffmpeg.

## How do I fix CVE-2026-70631?

Upgrade to a fixed version.

## Is CVE-2026-70631 being exploited?

There is no known exploitation of CVE-2026-70631 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-2026-70631 and fix it if it is affected.

What it is: CVE-2026-70631 is a medium-severity vulnerability in Ffmpeg Ffmpeg, published on 6 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-70631 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-2026-70631/ (Markdown: https://insights.sbomify.com/CVE-2026-70631/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70631
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70631
- OSV: https://osv.dev/vulnerability/CVE-2026-70631

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-70631/
Summaries are generated and may contain mistakes; the official description above is the record.