---
id: "CVE-2026-125269"
page: "https://infrastack.ai/live/CVE-2026-125269"
kind: "vulnerability"
aliases: ["CVE-2026-125269"]
title: "FFmpeg: crafted H.264 stream triggers double free, corrupting heap memory"
severity: "high"
cvss: 7.3
epss: null
exploited: false
status: "open"
category: "runtime"
products: [{"name": "FFmpeg", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["ffmpeg", "h264", "media-processing", "runtime"]
not_affected_if: ["filter-not-used", "trusted-input-only"]
published_at: "2026-11-09T20:18:13+00:00"
first_seen_at: "2026-11-09T20:48:14+00:00"
updated_at: "2026-11-09T20:49:44+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125269", "first_seen_at": "2026-11-09T20:48:14+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted H.264 stream triggers double free, corrupting heap memory

Link for people: https://infrastack.ai/live/CVE-2026-125269 (this .md is for agents)

FFmpeg through 9.0.2 has a double free in its SEI handling code, reachable when h264_metadata processes a crafted H.264 stream with display orientation SEI and extension data. An attacker who gets such a file processed can corrupt heap memory, which can lead to code execution.

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

## Affected

- vendor:FFmpeg affected range not listed fixed no fixed version listed

## How to check

- Check the installed FFmpeg version with `ffmpeg -version` and compare it to the fixed release in the product data (sources list FFmpeg through 9.0.2 as affected)
- Look for workflows that run `h264_metadata` with `display_orientation=insert` on untrusted input

## Fix

- FFmpeg: unknown (sources name the patch on github.com but do not state the fixed version)

## Timeline

- 2026-11-09T20:48:14+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125269

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-double-free-via-cbs-sei-delete-message-in-cbs-sei-c
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/2c515eea07df719379e7f73deeeb7ccb8768433f

## From the sources

FFmpeg through 9.0.2 contains a double free vulnerability in libavcodec/cbs_sei.c where cbs_sei_delete_message() leaves a stale extension_data reference that ff_cbs_sei_add_message() reuses. Attackers can supply a crafted H.264 stream with a display orientation SEI message followed by payload extension data, processed by h264_metadata with display_orientation=insert, to corrupt heap memory.

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