---
id: CVE-2026-112898
title: 'Pillow: Image.quantize() with empty palette leaks uninitialized stack memory'
summary: >-
  Pillow is a Python imaging library. From 9.1.0 until 13.0.0, Pillow can
  disclose uninitialized stack memory when Image.quantize() uses an empty
  palette. ImagingPaletteCacheUpdate() leaves a local cache array uninitialized
  when the palett…
severity: medium
cvss: 6.9
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-457
vendor: python-pillow
product: Pillow
affected:
  - 'Pillow >= 9.1.0, < 13.0.0'
published: '2026-10-19'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T22:04:23.462Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-112898'
references:
  - url: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-rfgq-q3w2-pmv2
    label: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-rfgq-q3w2-pmv2
  - url: >-
      https://github.com/python-pillow/Pillow/commit/13943c8f857b22f073d30f0ef9b725a0d255f1a4
    label: >-
      https://github.com/python-pillow/Pillow/commit/13943c8f857b22f073d30f0ef9b725a0d255f1a4
  - 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: '2026-10-19T22:46:42.318Z'
---

## Overview

Pillow is a Python imaging library. From 9.1.0 until 13.0.0, Pillow can disclose uninitialized stack memory when Image.quantize() uses an empty palette. ImagingPaletteCacheUpdate() leaves a local cache array uninitialized when the palette has zero entries, and the conversion path emits those bytes as output pixel indices. An attacker who controls the palette image can obtain stack contents from a returned PNG or GIF. This can disclose addresses and stack-canary data without an out-of-bounds access, memory corruption, or process crash. 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.