---
id: "CVE-2026-119205"
kind: "vulnerability"
aliases: ["CVE-2026-119205"]
title: "pypdf: crafted PDF can hang cloning and duplication, causing denial of service"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "pypdf", "python"]
not_affected_if: ["pypdf-not-used", "trusted-pdfs-only"]
published_at: "2026-10-29T21:17:19+00:00"
first_seen_at: "2026-10-29T21:26:51+00:00"
updated_at: "2026-10-29T21:28:41+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-119205", "first_seen_at": "2026-10-29T21:26:51+00:00"}]
---

# pypdf: crafted PDF can hang cloning and duplication, causing denial of service

pypdf, a pure-Python PDF library, can enter an infinite loop when cloning or duplicating a crafted cyclic dictionary object in a PDF. An attacker who supplies such a file can make the processing code hang, stalling the program that handles it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed pypdf version with `pip show pypdf` and look for anything below `6.21.4`.
- Search dependency files (requirements.txt, poetry.lock, uv.lock) for pypdf to find where it is pinned.

## Fix

- pypdf: upgrade to `6.21.4`

## Timeline

- 2026-10-29T21:26:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-119205

## From the sources

pypdf is a free and open-source pure-python PDF library. Prior to 6.21.4, pypdf can enter an infinite loop when cloning or duplicating a crafted cyclic DictionaryObject. Clone traversal checked generated destination references rather than the original source references, allowing some source cycles to evade the visited-object check. This issue is fixed in version 6.21.4.

---

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