CVE-2020-23879
📋 TL;DR
CVE-2020-23879 is a NULL pointer dereference vulnerability in pdf2json v0.71 that can cause denial of service (DoS) through application crashes. This affects any system or application using the vulnerable pdf2json library to parse PDF files. Attackers can exploit this by providing specially crafted PDF files to trigger the crash.
💻 Affected Systems
- pdf2json
📦 What is this software?
Pdf2json by Flowpaper
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service through application crash, potentially disrupting PDF processing services and causing system instability.
Likely Case
Application crash when processing malicious PDF files, leading to service interruption and potential data loss in processing queues.
If Mitigated
Application restart required after crash, with potential loss of in-process PDF conversions but no remote code execution.
🎯 Exploit Status
Proof of concept available on GitHub showing crash trigger. Exploitation requires only PDF file submission to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after 0.71 (check latest release)
Vendor Advisory: https://github.com/flexpaper/pdf2json/issues/44
Restart Required: Yes
Instructions:
1. Check current pdf2json version. 2. Update to latest version from GitHub repository. 3. Rebuild and redeploy any applications using pdf2json. 4. Restart affected services.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict PDF file validation before passing to pdf2json parser
Process isolation
linuxRun pdf2json in isolated containers or processes with automatic restart on crash
docker run --restart=always [your_pdf2json_container]
🧯 If You Can't Patch
- Implement strict file upload restrictions and PDF validation before processing
- Deploy monitoring and automatic restart mechanisms for pdf2json processes
🔍 How to Verify
Check if Vulnerable:
Check if pdf2json version is 0.71: 'pdf2json --version' or check package/installation versionCheck Version:
pdf2json --version 2>&1 | grep -i versionVerify Fix Applied:
Test with known malicious PDF from PoC repository after update - application should not crash📡 Detection & Monitoring
Log Indicators:
- Application crash logs
- Segmentation fault errors
- Unexpected process termination
Network Indicators:
- Multiple PDF uploads followed by service interruption
- Failed PDF processing requests
SIEM Query:
source="application.logs" AND ("segmentation fault" OR "null pointer" OR "pdf2json crash")