CVE-2026-22690
📋 TL;DR
This vulnerability in pypdf allows attackers to craft malicious PDF files that cause excessive processing time when parsed in non-strict mode. The attack works by omitting the /Root entry while using large /Size values, leading to potentially long runtimes for invalid files. This affects any application using pypdf versions before 6.6.0 to process untrusted PDF files.
💻 Affected Systems
- pypdf
📦 What is this software?
Pypdf by Pypdf Project
⚠️ Risk & Real-World Impact
Worst Case
Denial of service through resource exhaustion - malicious PDFs could cause pypdf processes to consume excessive CPU/time, potentially crashing applications or making services unavailable.
Likely Case
Degraded performance or temporary unavailability of services processing PDFs, requiring manual intervention to terminate hung processes.
If Mitigated
Minimal impact if strict mode is used or input validation prevents processing of malformed PDFs.
🎯 Exploit Status
Exploitation requires only crafting a malformed PDF file. No authentication or special privileges needed if application processes PDFs.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.6.0
Vendor Advisory: https://github.com/py-pdf/pypdf/security/advisories/GHSA-4xc4-762w-m6cg
Restart Required: No
Instructions:
1. Update pypdf using pip: 'pip install --upgrade pypdf==6.6.0' 2. Verify the update with: 'pip show pypdf' 3. Test PDF processing functionality after update.
🔧 Temporary Workarounds
Enable strict mode
allUse strict=True parameter when creating PdfReader objects to reject malformed PDFs early
reader = PdfReader(pdf_file, strict=True)
Input validation
allValidate PDF files before processing, checking for basic structure and size limits
🧯 If You Can't Patch
- Implement strict mode for all PDF processing (reader = PdfReader(file, strict=True))
- Add timeout mechanisms for PDF processing operations
- Limit PDF file sizes and implement rate limiting for PDF uploads/processing
🔍 How to Verify
Check if Vulnerable:
Check pypdf version with: 'python -c "import pypdf; print(pypdf.__version__)"' or 'pip show pypdf'Check Version:
python -c "import pypdf; print(pypdf.__version__)"Verify Fix Applied:
Confirm version is 6.6.0 or higher using version check command📡 Detection & Monitoring
Log Indicators:
- Long-running PDF processing tasks
- High CPU usage by Python processes handling PDFs
- Application timeouts or crashes during PDF parsing
Network Indicators:
- Multiple large PDF uploads to web applications
- Unusual PDF file patterns in upload traffic
SIEM Query:
Process logs showing python processes with high CPU duration (>30s) AND command containing 'pypdf' or PDF-related operations