Memory Exhaustion in PyPDF Image Parsing

Executive Summary

CVE-2026-59938 is a vulnerability in the pypdf library prior to version 6.14.0 where an attacker can craft a PDF file with image size values declared much larger than the actual image data. This causes the library to allocate excessive memory during image parsing, leading to potential resource exhaustion.

The issue arises because the library does not limit the requested image size, allowing malicious PDFs to trigger large memory usage. This vulnerability was fixed in version 6.14.0 by introducing a maximum buffer size limit for images, preventing excessive memory allocation.

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Impact Analysis

This vulnerability can lead to denial-of-service (DoS) attacks by causing the application using pypdf to consume excessive memory when processing maliciously crafted PDF files.

Such excessive memory usage can result in system slowdowns, crashes, or unavailability of services that rely on pypdf for PDF processing.

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Detection Guidance

This vulnerability involves processing maliciously crafted PDF files with image size declarations that are excessively large compared to the actual data, causing high memory usage during image parsing in pypdf versions prior to 6.14.0.

To detect this vulnerability on your system, you can check the version of the pypdf library installed. If it is older than 6.14.0, your system is potentially vulnerable.

Suggested commands to check the installed pypdf version:

• pip show pypdf
• pip list | grep pypdf

Additionally, monitoring for unusually high memory usage or crashes when processing PDF files with images could indicate exploitation attempts.

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Mitigation Strategies

The primary mitigation step is to upgrade the pypdf library to version 6.14.0 or later, where the vulnerability has been fixed by enforcing limits on image size during parsing.

If upgrading immediately is not possible, applying the patch from pull request #3888 can serve as a temporary workaround. This patch introduces a maximum buffer size limit for images to prevent excessive memory allocation.

In general, avoid processing untrusted PDF files or implement additional input validation and resource monitoring to detect and prevent potential denial-of-service conditions.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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