---
id: CVE-2026-70631
title: >-
  FFmpeg versions from 0.5 up to, but not including, 9.0 contain an
  uninitialized heap memory disclosure vulnerability in the native TIFF decoder
  in libavcodec/tiff.c
summary: >-
  FFmpeg versions from 0.5 up to, but not including, 9.0 contain an
  uninitialized heap memory disclosure vulnerability in the native TIFF decoder
  in libavcodec/tiff.c. An attacker who can cause FFmpeg to decode a crafted
  TIFF file can supp…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N'
cwe:
  - CWE-908
published: '2026-08-06'
updated: '2026-08-08'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-70631'
references:
  - url: >-
      https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/2f234ea34c81288e3840fca632dd16481d8de39f
    label: disclosure@vulncheck.com
  - url: >-
      https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/3c287af3affe1286350faa69c02bcc5d49de18bb
    label: disclosure@vulncheck.com
  - url: >-
      https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/a991b1fecbd8c9e6f4fc31c191bd12e4be27dbf7
    label: disclosure@vulncheck.com
  - url: 'https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23899'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/ffmpeg-uninitialized-heap-memory-read-in-tiff-decoder
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00178
epssPercentile: 0.06491
ingestedAt: '2026-08-09T01:31:46.481Z'
---

## Overview

FFmpeg versions from 0.5 up to, but not including, 9.0 contain an uninitialized heap memory disclosure vulnerability in the native TIFF decoder in libavcodec/tiff.c. An attacker who can cause FFmpeg to decode a crafted TIFF file can supply a valid Deflate-compressed strip that terminates successfully after producing fewer bytes than the declared strip requires. The tiff_unpack_zlib() function allocates a heap buffer sized for the full declared strip but copies all declared rows via memcpy() regardless of how many bytes zlib actually decompressed, causing unwritten bytes that can contain stale data from prior heap allocations to be incorporated into decoded image output and potentially exposing sensitive data in persistent services.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.