---
id: CVE-2026-96641
title: >-
  Pillow: Reachable undefined behavior in native integer operations, potentially
  leading to denial of service or logic integrity compromise
summary: >-
  Pillow is a Python imaging library. Prior to 13.0.0, PILfont text-width
  accumulation in src/_imaging.c checks positive glyph advances against INT_MAX
  but does not check negative advances against INT_MIN. Repeating a signed
  16-bit advance…
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-190
vendor: python-pillow
product: Pillow
affected:
  - Pillow < 13.0.0
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-28T01:50:02.182605Z'
exploitAvailable: true
published: '2026-10-21'
updated: '2026-10-28'
sourceUpdated: '2026-10-28T01:50:42.160Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-96641'
references:
  - url: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-4rm8-3hmm-39fg
    label: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-4rm8-3hmm-39fg
  - url: 'https://github.com/python-pillow/Pillow/pull/10010'
    label: 'https://github.com/python-pillow/Pillow/pull/10010'
  - url: >-
      https://github.com/python-pillow/Pillow/commit/80de4be9e38d3a6148dd4d8491eb80cd12b760a4
    label: >-
      https://github.com/python-pillow/Pillow/commit/80de4be9e38d3a6148dd4d8491eb80cd12b760a4
  - url: 'https://github.com/python-pillow/Pillow/releases/tag/13.0.0'
    label: 'https://github.com/python-pillow/Pillow/releases/tag/13.0.0'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-96641'
  - url: 'https://github.com/python-pillow/Pillow'
  - url: 'https://github.com/advisories/GHSA-4rm8-3hmm-39fg'
tags:
  - cve.org
  - exploit-available
  - osv
  - pip
  - ghsa
epss: 0.0035
epssPercentile: 0.28472
aliases:
  - GHSA-4rm8-3hmm-39fg
ecosystem: pip
patched:
  - pillow 13.0.0
ingestedAt: '2026-10-21T21:13:32.870Z'
---

## Overview

Pillow is a Python imaging library. Prior to 13.0.0, PILfont text-width accumulation in src/_imaging.c checks positive glyph advances against INT_MAX but does not check negative advances against INT_MIN. Repeating a signed 16-bit advance of -32768 can therefore execute a signed C integer overflow in xsize += dx, producing a large positive width from a negative mathematical result. Applications that use getlength(), getsize(), or derived layout, quota, serialization, or allocation calculations can experience logic-integrity errors or resource consumption, while the high-level mask path commonly retains a decompression-bomb check. This issue is fixed in version 13.0.0.

## Affected

- `Pillow < 13.0.0`

## Remediation

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

## Package advisory (CVE-2026-96641)

Affected packages:

- `pillow < 13.0.0`

Patched in:

- `pillow 13.0.0`

Source: https://osv.dev/vulnerability/GHSA-4rm8-3hmm-39fg