---
id: CVE-2026-84309
title: pypdf is a free and open-source pure-python PDF library
summary: >-
  pypdf is a free and open-source pure-python PDF library. Prior to 6.16.0, an
  attacker can craft a PDF whose cyclic tree structure causes
  pypdf/generic/_data_structures.py TreeObject.insert_child to follow /Next
  links indefinitely when a …
severity: medium
cwe:
  - CWE-835
vendor: pypdf
product: pypdf
affected:
  - pypdf < 6.16.0
patched:
  - pypdf 6.16.0
published: '2026-09-01'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T16:49:20.627'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-84309'
references:
  - url: >-
      https://github.com/py-pdf/pypdf/commit/c9ba557d565d57c53a0b3a0be06c0a4c29b0559b
    label: security-advisories@github.com
  - url: 'https://github.com/py-pdf/pypdf/pull/3964'
    label: security-advisories@github.com
  - url: 'https://github.com/py-pdf/pypdf/releases/tag/6.16.0'
    label: security-advisories@github.com
  - url: 'https://github.com/py-pdf/pypdf/security/advisories/GHSA-jp53-mhqp-8xcg'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-jp53-mhqp-8xcg'
  - url: 'https://github.com/py-pdf/pypdf'
  - url: 'https://pypi.org/project/pypdf'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-84309'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84309.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-84309'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2527430'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-84309'
tags:
  - nvd
  - ghsa
  - pip
  - osv
  - csaf
  - vex
  - red-hat
epss: 0.0018
epssPercentile: 0.06682
aliases:
  - GHSA-jp53-mhqp-8xcg
  - PYSEC-2026-3913
ecosystem: pip
ingestedAt: '2026-09-01T21:32:41.514Z'
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'
cvssSource: vendor
---

## Overview

pypdf is a free and open-source pure-python PDF library. Prior to 6.16.0, an attacker can craft a PDF whose cyclic tree structure causes pypdf/generic/_data_structures.py TreeObject.insert_child to follow /Next links indefinitely when a writing code path inserts a child, producing an infinite loop. This issue is fixed in version 6.16.0.

## Remediation

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

## Package advisory (CVE-2026-84309)

Affected packages:

- `pypdf < 6.16.0`

Patched in:

- `pypdf 6.16.0`

Source: https://github.com/advisories/GHSA-jp53-mhqp-8xcg

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Ansible Automation Orchestrator 2026, Exploit Intelligence, Lightspeed Core, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux AI (RHEL AI) 3, … · no fix planned: Exploit Intelligence, Red Hat Ansible Automation Platform 2, Red Hat Quay 3, Ansible Automation Orchestrator 2026, … · updated 2026-09-25 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84309.json)