---
id: "CVE-2026-125243"
page: "https://infrastack.ai/live/CVE-2026-125243"
kind: "vulnerability"
aliases: ["CVE-2026-125243"]
title: "FFmpeg: crafted JPEG-LS image leaks leftover heap memory in decoded frames"
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-jpegls-input"]
published_at: "2026-11-09T19:17:02+00:00"
first_seen_at: "2026-11-09T19:28:20+00:00"
updated_at: "2026-11-09T19:32:13+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125243", "first_seen_at": "2026-11-09T19:28:20+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted JPEG-LS image leaks leftover heap memory in decoded frames

Link for people: https://infrastack.ai/live/CVE-2026-125243 (this .md is for agents)

FFmpeg's JPEG-LS decoder mishandles 16-bit line-interleaved scans by decoding them as 8-bit samples. A crafted single-component JPEG-LS image makes decoded GRAY16 frames expose uninitialized heap memory.

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

## Timeline

- 2026-11-09T19:28:20+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125243

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-memory-disclosure-via-jpeg-ls-decoder
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/60bc31fcf6543505e6d2fc1a9399cca95f54ba4d

## From the sources

FFmpeg through 9.0.2 contains an uninitialized memory disclosure vulnerability in ff_jpegls_decode_picture() in libavcodec/jpeglsdec.c, which decodes 16-bit line-interleaved JPEG-LS scans as 8-bit samples. Attackers can supply a crafted single-component JPEG-LS image with the ILV byte set to 1, causing decoded GRAY16 frames to expose leftover heap memory.

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