---
id: CVE-2026-96638
title: >-
  Pillow: BMP RLE decoder memory-amplification DoS via unbounded delta escape /
  absolute mode
summary: >-
  Pillow is a Python imaging library. From 9.1.0 until 13.0.0,
  BmpRleDecoder.decode() in src/PIL/BmpImagePlugin.py permits crafted RLE BMP
  delta escapes and absolute-mode runs to append beyond the remaining
  dest_length without a per-branch…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-400
  - CWE-770
vendor: python-pillow
product: Pillow
affected:
  - 'Pillow >= 9.1.0, < 13.0.0'
published: '2026-10-21'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T20:47:21.767Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-96638'
references:
  - url: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-24rc-8hj2-v98c
    label: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-24rc-8hj2-v98c
  - url: 'https://github.com/python-pillow/Pillow/pull/10015'
    label: 'https://github.com/python-pillow/Pillow/pull/10015'
  - url: >-
      https://github.com/python-pillow/Pillow/commit/e7794835e323ff2691d9b3a974cade1a44301b9a
    label: >-
      https://github.com/python-pillow/Pillow/commit/e7794835e323ff2691d9b3a974cade1a44301b9a
  - url: 'https://github.com/python-pillow/Pillow/releases/tag/13.0.0'
    label: 'https://github.com/python-pillow/Pillow/releases/tag/13.0.0'
tags:
  - cve.org
ingestedAt: '2026-10-21T21:13:32.882Z'
---

## Overview

Pillow is a Python imaging library. From 9.1.0 until 13.0.0, BmpRleDecoder.decode() in src/PIL/BmpImagePlugin.py permits crafted RLE BMP delta escapes and absolute-mode runs to append beyond the remaining dest_length without a per-branch cap. A delta can add roughly 255 image rows in one iteration, so a kilobyte-sized file with a large but permitted width can expand the data bytearray to hundreds of megabytes or more, causing memory-exhaustion denial of service. This issue is fixed in version 13.0.0.

## Affected

- `Pillow >= 9.1.0, < 13.0.0`

## Remediation

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