---
id: "CVE-2026-113790"
kind: "vulnerability"
aliases: ["CVE-2026-113790", "GHSA-f54x-cmq8-qg57"]
title: "pypdf: Possible large memory usage when parsing arrays and dictionaries"
severity: "medium"
cvss: 6.0
epss: 0.003169999923557043
exploited: false
status: "open"
category: "package"
products: [{"name": "pypdf", "fixed": ["6.21.0"], "affected": "< 6.21.0", "ecosystem": "pypi"}]
ecosystems: ["pypi"]
tags: ["cwe-400", "document-processing", "package", "pypdf", "python"]
not_affected_if: ["no-untrusted-pdf-input", "pypdf-6.21.0-or-later"]
published_at: "2026-10-21T16:17:26+00:00"
first_seen_at: "2026-10-23T19:11:31+00:00"
updated_at: "2026-10-23T21:57:29+00:00"
sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-f54x-cmq8-qg57", "first_seen_at": "2026-10-23T19:11:31+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113790", "first_seen_at": "2026-10-23T21:57:29+00:00"}]
---

# pypdf: Possible large memory usage when parsing arrays and dictionaries

pypdf versions before 6.21.0 can use large amounts of memory when parsing a crafted PDF with arrays or dictionaries containing many elements. An attacker who supplies such a PDF can exhaust memory and cause a denial of service in the process parsing it.

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

## Affected

- pypi:pypdf affected < 6.21.0 fixed 6.21.0

## How to check

pip show pypdf (or check the lockfile) and look for a version below 6.21.0

## Fix

Upgrade pypdf to 6.21.0 or later.
If upgrading is not possible, apply the changes from PR #4218 in the pypdf repository.

## Timeline

- 2026-10-23T19:11:31+00:00 ghsa https://github.com/advisories/GHSA-f54x-cmq8-qg57
- 2026-10-23T21:57:29+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-113790

## From the sources

### Impact

An attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing arrays and/or dictionaries with lots of elements.

### Patches

This has been fixed in [pypdf==6.21.0](https://github.com/py-pdf/pypdf/releases/tag/6.21.0).

### Workarounds

If you cannot upgrade yet, consider applying the changes from PR [#4218](https://github.com/py-pdf/pypdf/pull/4218).

---

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