---
id: "CVE-2026-125191"
page: "https://infrastack.ai/live/CVE-2026-125191"
kind: "vulnerability"
aliases: ["CVE-2026-125191"]
title: "FFmpeg: crafted video streams make the V4L2 decoder hang forever"
severity: "medium"
cvss: 5.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["ffmpeg", "libavcodec", "linux", "media-processing", "package", "v4l2"]
not_affected_if: ["no-untrusted-input", "software-decoding-only"]
published_at: "2026-11-09T19:16:54+00:00"
first_seen_at: "2026-11-09T19:28:17+00:00"
updated_at: "2026-11-09T19:32:04+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125191", "first_seen_at": "2026-11-09T19:28:17+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted video streams make the V4L2 decoder hang forever

Link for people: https://infrastack.ai/live/CVE-2026-125191 (this .md is for agents)

FFmpeg's V4L2 mem2mem decoder leaks a reference count in libavcodec/v4l2_buffers.c. A crafted H.264, HEVC, or VP9 stream with resolution changes makes the decoder wait forever, hanging the application that decodes it.

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

## How to check

- Check whether the FFmpeg build includes the V4L2 mem2mem decoders (for example `ffmpeg -decoders | grep v4l2m2m`)
- Check the FFmpeg version with `ffmpeg -version`; the sources say FFmpeg through 9.0.2 is affected
- Check whether the application decodes untrusted video with hardware acceleration enabled

## Fix

- FFmpeg: unknown; the sources do not name a fixed version
- A patch is linked from the sources (github.com), but its content was not read

## Timeline

- 2026-11-09T19:28:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125191

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-v4l2-m2m-decoder-deadlock-via-reference-count-leak
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/4d2d58efa9b9f3802893b1db0ea1edfbe1cc66ef

## From the sources

FFmpeg through 9.0.2 contains a reference count leak in libavcodec/v4l2_buffers.c that allows attackers to deadlock the V4L2 mem2mem decoder on multi-plane capture formats. Attackers can supply crafted H.264, HEVC, or VP9 streams with resolution changes, making ff_v4l2_m2m_codec_reinit() wait forever and hang the decoding application.

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