---
id: "CVE-2026-115572"
kind: "vulnerability"
aliases: ["CVE-2026-115572", "GHSA-6c7f-9265-g8fw"]
title: "pypdf: Possible long runtimes for repeated references to the same missing object"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "pypdf", "fixed": ["6.21.2"], "affected": "< 6.21.2", "ecosystem": "pypi"}]
ecosystems: ["pypi"]
tags: ["cwe-400", "package", "pdf-processing", "pypdf", "python"]
not_affected_if: ["no-untrusted-pdfs", "pypdf-6.21.2-or-later", "pypdf-not-installed"]
published_at: "2026-10-23T20:17:20+00:00"
first_seen_at: "2026-10-23T20:59:05+00:00"
updated_at: "2026-10-23T21:57:34+00:00"
sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-6c7f-9265-g8fw", "first_seen_at": "2026-10-23T20:59:05+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115572", "first_seen_at": "2026-10-23T21:57:34+00:00"}]
---

# pypdf: Possible long runtimes for repeated references to the same missing object

pypdf, a Python PDF library, takes a very long time to process a crafted PDF that references the same missing object many times. An attacker who gets such a file in front of your parser can tie up CPU and stall the worker (denial of service).

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

## Affected

- pypi:pypdf affected < 6.21.2 fixed 6.21.2

## How to check

pip show pypdf (or check requirements/lock files) and look for a version below 6.21.2.

## Fix

Upgrade pypdf to 6.21.2 or later.
If you cannot upgrade yet, apply the changes from PR #4240 (https://github.com/py-pdf/pypdf/pull/4240).

## Timeline

- 2026-10-23T20:59:05+00:00 ghsa https://github.com/advisories/GHSA-6c7f-9265-g8fw
- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115572

## From the sources

### Impact

An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires loading relevant parts of a file (like their pages) where the same, but non-existent indirect object is referenced multiple times.

### Patches

This has been fixed in [pypdf==6.21.2](https://github.com/py-pdf/pypdf/releases/tag/6.21.2).

### Workarounds

If you cannot upgrade yet, consider applying the changes from PR [#4240](https://github.com/py-pdf/pypdf/pull/4240).

---

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