---
id: "CVE-2026-125098"
page: "https://infrastack.ai/live/CVE-2026-125098"
kind: "vulnerability"
aliases: ["CVE-2026-125098"]
title: "FFmpeg: crafted WebP image leaks stale pixel memory from earlier frames"
severity: "medium"
cvss: 4.8
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["ffmpeg", "libavcodec", "media-processing", "runtime", "webp"]
not_affected_if: ["no-webp-decoding", "trusted-input-only"]
published_at: "2026-11-09T19:16:50+00:00"
first_seen_at: "2026-11-09T19:28:15+00:00"
updated_at: "2026-11-09T19:33:35+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125098", "first_seen_at": "2026-11-09T19:28:15+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted WebP image leaks stale pixel memory from earlier frames

Link for people: https://infrastack.ai/live/CVE-2026-125098 (this .md is for agents)

FFmpeg's WebP decoder in libavcodec leaves the alpha plane uninitialized when a WebP image has a short uncompressed ALPH chunk. An attacker who supplies such an image can read stale pixel data left over from previously decoded frames.

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

## How to check

- Run `ffmpeg -version` and compare against the fixed release named in the linked patch.
- Check whether the WebP decoder is used on untrusted images in your pipeline.

## Timeline

- 2026-11-09T19:28:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125098

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-webp-decoder-information-disclosure-via-short-alph-chunk
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/92b318e0b33623720d9f128ad7bc5fa8277c34f7

## From the sources

FFmpeg through 9.0.2 contains an information disclosure vulnerability in vp8_lossy_decode_alpha() in libavcodec/webp.c that leaves alpha plane memory uninitialized for short uncompressed ALPH chunks. Attackers can supply a crafted WebP image whose ALPH chunk is shorter than width * height to disclose stale pixel data from previously decoded frames.

---

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