---
id: CVE-2026-42310
aliases:
  - GHSA-r73j-pqj5-w3x7
  - BIT-pillow-2026-42310
  - PYSEC-2026-2874
title: Pillow has a PDF Parsing Trailer Infinite Loop (DoS)
summary: Pillow has a PDF Parsing Trailer Infinite Loop (DoS)
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
vendor: pillow
product: pillow
ecosystem: pip
affected:
  - 'pillow >= 4.2.0, < 12.2.0'
patched:
  - pillow 12.2.0
published: '2026-05-04'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:55.309086884Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-r73j-pqj5-w3x7'
references:
  - url: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-r73j-pqj5-w3x7
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-42310'
  - url: 'https://github.com/python-pillow/Pillow/pull/9519'
  - url: >-
      https://github.com/python-pillow/Pillow/commit/3bf614e4b8615d0ce1d5039efaf6db447fe7c468
  - url: 'https://github.com/python-pillow/Pillow'
  - url: 'https://github.com/python-pillow/Pillow/releases/tag/12.2.0'
tags:
  - osv
  - pip
epss: 0.00177
epssPercentile: 0.06477
ingestedAt: '2026-07-13T18:58:02.525Z'
---

## Overview

### Impact
An attacker can supply a malicious PDF that causes the process to hang indefinitely, consuming 100% CPU and making the application unresponsive.

### Patches
Patched version: 12.2.0.

PdfParser (introduced in Pillow 4.2.0) follows Prev pointers in PDF trailers to read cross-reference sections. If a
trailer's Prev pointer references an offset that has already been processed — either pointing to itself or forming a
longer cycle — the parser enters an infinite loop. Pillow now tracks previously processed trailer offsets and raises an
error if a cycle is detected.

### Workarounds
Use any version but the affected versions: >= 4.2.0, < 12.2.0

### Resources
 - Fix: https://github.com/python-pillow/Pillow/pull/9519

## Affected packages

- `pillow >= 4.2.0, < 12.2.0`

## Remediation

Upgrade to a patched release:

- `pillow 12.2.0`