---
id: "CVE-2026-125176"
page: "https://infrastack.ai/live/CVE-2026-125176"
kind: "vulnerability"
aliases: ["CVE-2026-125176"]
title: "FFmpeg: crafted Flash Screen Video file leaks heap memory into output"
severity: "medium"
cvss: 4.8
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["ffmpeg", "media-processing", "runtime", "transcoding"]
not_affected_if: ["managed-hosting", "no-flsv2-input"]
published_at: "2026-11-09T19:16:52+00:00"
first_seen_at: "2026-11-09T19:28:16+00:00"
updated_at: "2026-11-09T19:32:23+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125176", "first_seen_at": "2026-11-09T19:28:16+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted Flash Screen Video file leaks heap memory into output

Link for people: https://infrastack.ai/live/CVE-2026-125176 (this .md is for agents)

FFmpeg through 9.0.2 reads past decompressed data in the flashsv decoder when a Flash Screen Video 2 block ends mid-pixel. An attacker who supplies such a file can leak heap memory into the decoded video frames.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed FFmpeg version with `ffmpeg -version`
- Look for a build that includes libavcodec/flashsv.c if you compile FFmpeg yourself

## Fix

- FFmpeg through `9.0.2` is affected; the sources do not state a fixed version
- Patch linked from the NVD record (github.com); the sources do not state the version

## Timeline

- 2026-11-09T19:28:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125176

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-memory-read-in-flash-screen-video-2-decoder
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/16d0f7f408ba47b4091a22109d4f22f5fd57820a

## From the sources

FFmpeg through 9.0.2 contains an uninitialized memory read vulnerability in decode_hybrid() in libavcodec/flashsv.c that reads past decompressed data when decoding 15-bit color pixels. Attackers can supply a crafted Flash Screen Video 2 block whose inflated data ends mid-pixel to leak heap memory into decoded output frames.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_