---
id: "CVE-2026-125266"
page: "https://infrastack.ai/live/CVE-2026-125266"
kind: "vulnerability"
aliases: ["CVE-2026-125266"]
title: "FFmpeg: crafted SANM animation leaks decoder stack memory into video"
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", "sanm-not-decoded"]
published_at: "2026-11-09T20:18:13+00:00"
first_seen_at: "2026-11-09T20:48:14+00:00"
updated_at: "2026-11-09T20:50:00+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-125266", "first_seen_at": "2026-11-09T20:48:14+00:00"}]
exploit_sources: []
---

# FFmpeg: crafted SANM animation leaks decoder stack memory into video

Link for people: https://infrastack.ai/live/CVE-2026-125266 (this .md is for agents)

FFmpeg through 9.0.2 has an uninitialized stack memory read in the old_codec23() decoder in libavcodec/sanm.c. A crafted LucasArts SMUSH/SANM file using codec 23 can leak stack bytes into decoded output video.

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

## Timeline

- 2026-11-09T20:48:14+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-125266

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-stack-memory-disclosure-via-sanm-codec-23
- [fix] Patch: github.com https://github.com/FFmpeg/FFmpeg/commit/d42cb1925987cc27899441ce39fa7bd2647dc72e

## From the sources

FFmpeg through 9.0.2 contains an uninitialized stack memory disclosure vulnerability in old_codec23() of libavcodec/sanm.c that leaks stack bytes into decoded frames. Attackers can supply a crafted LucasArts SMUSH/SANM animation using codec 23 with an inline table to expose decoder process stack memory in output video.

---

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