---
id: "CVE-2026-125220"
page: "https://infrastack.ai/live/CVE-2026-125220"
kind: "vulnerability"
aliases: ["CVE-2026-125220"]
title: "FFmpeg: crafted Mimic video file hangs frame-threaded decoding indefinitely"
severity: "medium"
cvss: 6.8
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["ffmpeg", "media-processing", "runtime", "self-hosted"]
not_affected_if: ["no-mimic-decoding", "trusted-input-only"]
published_at: "2026-11-09T19:16:59+00:00"
first_seen_at: "2026-11-09T19:28:19+00:00"
updated_at: "2026-11-09T19:31:25+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125220", "first_seen_at": "2026-11-09T19:28:19+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted Mimic video file hangs frame-threaded decoding indefinitely

Link for people: https://infrastack.ai/live/CVE-2026-125220 (this .md is for agents)

FFmpeg's Mimic video decoder fails to report frame progress when a frame is oversized, which can deadlock frame-threaded decoding. An attacker who supplies a crafted file can make decoding hang indefinitely, a denial of service.

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

## How to check

- Check the FFmpeg version with `ffmpeg -version`; versions through `9.0.2` are described as affected.
- Find services that decode untrusted media with FFmpeg, such as upload transcoders or thumbnail generators.

## Timeline

- 2026-11-09T19:28:19+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125220

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-mimic-decoder-deadlock-via-frame-threading-failure
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/db77b0b8318ddb38b5a3227724da088a325a4308

## From the sources

FFmpeg through 9.0.2 contains a deadlock vulnerability in mimic_decode_frame() in libavcodec/mimic.c that fails to report frame progress when init_get_bits8() fails. Attackers can supply a crafted file with an oversized Mimic intra frame followed by inter frames to hang frame-threaded decoding indefinitely.

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