CVE-2026-27025
📋 TL;DR
This vulnerability in pypdf allows attackers to craft malicious PDF files that cause excessive memory consumption and long processing times when parsing font /ToUnicode entries during text extraction. It affects all systems using pypdf versions before 6.7.1 for PDF processing. Users who process untrusted PDF files are particularly vulnerable.
💻 Affected Systems
- pypdf
📦 What is this software?
Pypdf by Pypdf Project
⚠️ Risk & Real-World Impact
Worst Case
Denial of service through resource exhaustion, potentially crashing applications or consuming all available memory on the system.
Likely Case
Degraded performance and increased resource usage when processing malicious PDFs, leading to application slowdowns or timeouts.
If Mitigated
Minimal impact with proper input validation and resource limits in place, though processing may still be slower.
🎯 Exploit Status
Exploitation is straightforward: create a PDF with specially crafted /ToUnicode font entries and trigger parsing.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.7.1
Vendor Advisory: https://github.com/py-pdf/pypdf/security/advisories/GHSA-wgvp-vg3v-2xq3
Restart Required: No
Instructions:
1. Update pypdf using pip: 'pip install --upgrade pypdf==6.7.1' 2. Verify the update with: 'pip show pypdf' 3. Test PDF processing functionality.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict validation of PDF files before processing, rejecting files with suspicious font entries.
Resource limiting
linuxSet memory and time limits for PDF parsing operations to prevent resource exhaustion.
import resource; resource.setrlimit(resource.RLIMIT_AS, (max_memory, max_memory))
🧯 If You Can't Patch
- Implement strict file upload controls and only accept PDFs from trusted sources.
- Isolate PDF processing in containerized environments with strict resource limits.
🔍 How to Verify
Check if Vulnerable:
Check pypdf version: 'pip show pypdf | grep Version' - if version is less than 6.7.1, system is vulnerable.Check Version:
pip show pypdf | grep VersionVerify Fix Applied:
After updating, verify version is 6.7.1 or higher and test processing known malicious PDF samples.📡 Detection & Monitoring
Log Indicators:
- Unusually high memory usage during PDF processing
- Long-running PDF parsing operations
- Application crashes or timeouts when handling PDFs
Network Indicators:
- Large PDF file uploads followed by increased server resource consumption
SIEM Query:
source="application.log" AND ("memory exhaustion" OR "PDF processing timeout" OR "pypdf")