---
id: "CVE-2026-125096"
page: "https://infrastack.ai/live/CVE-2026-125096"
kind: "vulnerability"
aliases: ["CVE-2026-125096"]
title: "FFmpeg: crafted Tiertex SEQ file leaks uninitialized stack memory into output"
severity: "medium"
cvss: 4.8
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["ffmpeg", "libavcodec", "media-processing", "package"]
not_affected_if: ["no-untrusted-media", "seq-decoder-unused"]
published_at: "2026-11-09T19:16:50+00:00"
first_seen_at: "2026-11-09T19:28:15+00:00"
updated_at: "2026-11-09T19:33:40+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125096", "first_seen_at": "2026-11-09T19:28:15+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted Tiertex SEQ file leaks uninitialized stack memory into output

Link for people: https://infrastack.ai/live/CVE-2026-125096 (this .md is for agents)

FFmpeg's Tiertex SEQ decoder copies an uninitialized 64-byte stack block into decoded frames when RLE unpacking fails. An attacker who supplies a crafted SEQ file can read stack contents in the visible output.

_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`; the sources say the flaw affects releases through `9.0.2`.
- Look for applications that decode untrusted Tiertex SEQ files with libavcodec.

## Fix

- The sources link a patch but do not state a fixed version. unknown

## Timeline

- 2026-11-09T19:28:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125096

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-memory-disclosure-via-tiertex-seq-decoder
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/c896bbb24535685509a816af09665cb73bf2d0c7

## From the sources

FFmpeg through 9.0.2 contains an uninitialized memory disclosure vulnerability in libavcodec/tiertexseqv.c that allows attackers to leak stack contents by triggering failed RLE unpacking. Attackers can supply a crafted Tiertex SEQ file so seq_decode_op1() copies an uninitialized 64-byte stack block into decoded frames, exposing stack memory in visible output.

---

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