CVE-2025-62707: Pypdf_project Pypdf DOS Vulnerability

CVE-2025-62707 Overview

CVE-2025-62707 is an Infinite Loop vulnerability affecting pypdf, a free and open-source pure-python PDF library. Prior to version 6.1.3, an attacker can craft a malicious PDF document that triggers an infinite loop condition, leading to a denial of service. The vulnerability is triggered when parsing the content stream of a page containing an inline image that uses the DCTDecode filter.

Critical Impact

Applications using vulnerable versions of pypdf can be rendered unresponsive when processing maliciously crafted PDF files, potentially causing service disruption for document processing pipelines and web applications that handle user-uploaded PDFs.

Affected Products

• pypdf versions prior to 6.1.3
• Applications and services using pypdf for PDF parsing and manipulation
• Python-based document processing systems leveraging pypdf library

Discovery Timeline

• 2025-10-22 - CVE-2025-62707 published to NVD
• 2025-10-27 - Last updated in NVD database

Technical Details for CVE-2025-62707

Vulnerability Analysis

This vulnerability is classified as CWE-834 (Excessive Iteration), which occurs when the software performs an excessive number of iterations, consuming resources without proper termination conditions. In the case of CVE-2025-62707, the pypdf library fails to properly handle certain edge cases when processing inline images within PDF content streams that utilize the DCTDecode filter.

The DCTDecode filter is used in PDFs to decompress JPEG-compressed data. When a malformed or specially crafted inline image using this filter is embedded in a PDF's content stream, the parsing logic enters an infinite loop state. This causes the application to consume CPU resources indefinitely without ever completing the parsing operation.

The attack can be executed remotely over the network by delivering a malicious PDF to any application that processes it using the vulnerable pypdf library. No authentication or user interaction beyond the normal document handling workflow is required.

Root Cause

The root cause lies in the content stream parsing logic within pypdf when handling inline images with the DCTDecode filter. The parser lacks proper boundary checking or termination conditions for certain malformed image data structures. When encountering a specially crafted inline image, the parsing routine continues iterating through data without reaching a valid exit condition, resulting in an infinite loop.

Attack Vector

The attack vector is network-based, where an attacker can deliver the malicious PDF through various channels such as email attachments, file uploads to web applications, document management systems, or any other mechanism that results in the target application parsing the PDF using pypdf. The vulnerability requires no special privileges or user authentication, making it accessible to unauthenticated attackers.

The exploitation scenario involves:

1. Attacker crafts a PDF with a malicious content stream containing an inline image using the DCTDecode filter
2. The malicious PDF is delivered to a system running a vulnerable version of pypdf
3. When the application parses the page content stream, the infinite loop is triggered
4. System resources are consumed, causing denial of service

Detection Methods for CVE-2025-62707

Indicators of Compromise

• Abnormally high CPU utilization by Python processes handling PDF operations
• Application processes stuck in unresponsive states while processing PDF files
• PDF files with suspicious inline image structures using DCTDecode filters
• Timeout errors in PDF processing workflows that previously functioned normally

Detection Strategies

• Monitor Python application processes for excessive CPU usage during PDF parsing operations
• Implement timeout mechanisms for PDF processing tasks to detect and terminate infinite loops
• Analyze incoming PDF files for unusual inline image structures before processing
• Review application logs for recurring failures or timeouts in PDF parsing functions

Monitoring Recommendations

• Set up alerting for processes exceeding CPU thresholds during document processing
• Implement watchdog timers for PDF parsing operations to detect hung processes
• Monitor pypdf library version deployments across your infrastructure
• Track document processing queue depths for abnormal backlogs indicating stuck operations

How to Mitigate CVE-2025-62707

Immediate Actions Required

• Upgrade pypdf to version 6.1.3 or later immediately across all affected systems
• Implement processing timeouts for PDF parsing operations as a defensive measure
• Review and audit all applications and services utilizing the pypdf library
• Consider implementing sandboxed PDF processing to limit resource consumption impact

Patch Information

The vulnerability has been fixed in pypdf version 6.1.3. The fix addresses the infinite loop condition in the content stream parsing logic when handling inline images with the DCTDecode filter. Organizations should update to this version or later to remediate the vulnerability.

For reference, the fix is available in the following resources:

• GitHub Commit with Fix
• Pull Request Discussion
• Release Notes for 6.1.3
• Security Advisory GHSA-vr63-x8vc-m265

Workarounds

• Implement strict timeouts for all PDF parsing operations to prevent resource exhaustion
• Add resource limits (CPU and memory) to containerized or sandboxed PDF processing environments
• Pre-validate PDF structure before processing with pypdf using alternative validation tools
• Consider temporary isolation of PDF processing functions until the patch can be applied

# Upgrade pypdf to the patched version
pip install --upgrade pypdf>=6.1.3

# Verify installed version
pip show pypdf | grep Version