---
id: CVE-2026-33123
aliases:
  - GHSA-qpxp-75px-xjcp
  - PYSEC-2026-3023
title: pypdf has inefficient decoding of array-based streams
summary: pypdf has inefficient decoding of array-based streams
severity: medium
vendor: pypdf
product: pypdf
ecosystem: pip
affected:
  - pypdf < 6.9.1
patched:
  - pypdf 6.9.1
published: '2026-03-18'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:51:00.643708515Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-qpxp-75px-xjcp'
references:
  - url: 'https://github.com/py-pdf/pypdf/security/advisories/GHSA-qpxp-75px-xjcp'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-33123'
  - url: 'https://github.com/py-pdf/pypdf/pull/3686'
  - url: 'https://github.com/py-pdf/pypdf'
  - url: 'https://github.com/py-pdf/pypdf/releases/tag/6.9.1'
tags:
  - osv
  - pip
epss: 0.00374
epssPercentile: 0.28572
ingestedAt: '2026-07-13T18:58:02.180Z'
---

## Overview

### Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes and/or large memory usage. This requires accessing an array-based stream with lots of entries.

### Patches
This has been fixed in [pypdf==6.9.1](https://github.com/py-pdf/pypdf/releases/tag/6.9.1).

### Workarounds
If you cannot upgrade yet, consider applying the changes from PR [#3686](https://github.com/py-pdf/pypdf/pull/3686).

## Affected packages

- `pypdf < 6.9.1`

## Remediation

Upgrade to a patched release:

- `pypdf 6.9.1`