CVE-2026-112898

Received Received - Intake

Pillow quantize uninitialized memory disclosure

Publication date: 2026-10-19

Last updated on: 2026-10-19

Assigner: GitHub, Inc.

Description

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-19

Last Modified

2026-10-19

Generated

2026-10-20

AI Q&A

2026-10-20

EPSS Evaluated

N/A

NVD

CVE-2026-112898

Affected Vendors & Products

Vendor	Product	Version / Range
python-pillow	Pillow	>= 9.1.0, < 13.0.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-457	The code uses a variable that has not been initialized, leading to unpredictable or unintended results.

Attack-Flow Graph

Executive Summary

Pillow is a Python imaging library. From versions 9.1.0 to 13.0.0, it can disclose uninitialized stack memory when Image.quantize() uses an empty palette. The function ImagingPaletteCacheUpdate() leaves a local cache array uninitialized if the palette has zero entries. This causes the conversion path to emit those bytes as output pixel indices, potentially exposing stack contents in returned PNG or GIF files.

Detection Guidance

This vulnerability can be detected by checking the version of Pillow installed on your system. Run 'pip show Pillow' or 'python -c "import PIL; print(PIL.__version__)"' to verify if the version is between 9.1.0 and 12.9.9. If so, the system is vulnerable.

Impact Analysis

An attacker who controls a palette image could exploit this to obtain sensitive stack memory contents, such as memory addresses or stack canary data. This could lead to information disclosure without requiring out-of-bounds access, memory corruption, or process crashes.

Mitigation Strategies

Upgrade Pillow to version 13.0.0 or later immediately. Use 'pip install --upgrade Pillow' or your package manager to update. If upgrading is not possible, avoid using Image.quantize() with untrusted input or empty palettes.

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