CVE-2020-16600
📋 TL;DR
This CVE describes a Use After Free vulnerability in the MuPDF library that occurs when processing PDF files with invalid pixmap dimensions. Attackers can exploit this to potentially execute arbitrary code or cause denial of service. Any application using vulnerable versions of MuPDF for PDF processing is affected.
💻 Affected Systems
- Artifex MuPDF library
- Applications embedding MuPDF
📦 What is this software?
Mupdf by Artifex
Mupdf by Artifex
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if exploited successfully.
Likely Case
Application crash or denial of service when processing malicious PDF files.
If Mitigated
Limited impact with proper sandboxing and memory protection mechanisms in place.
🎯 Exploit Status
Exploitation requires user to open a malicious PDF file. No public exploit code is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit 96751b25462f83d6e16a9afaf8980b0c3f979c8b and later versions
Vendor Advisory: http://git.ghostscript.com/?p=mupdf.git%3Bh=96751b25462f83d6e16a9afaf8980b0c3f979c8b
Restart Required: Yes
Instructions:
1. Update MuPDF to version after commit 96751b25462f83d6e16a9afaf8980b0c3f979c8b. 2. Rebuild applications using MuPDF. 3. Restart affected services.
🔧 Temporary Workarounds
Disable PDF processing
allTemporarily disable PDF processing in affected applications
Sandbox PDF processing
allRun PDF processing in isolated containers or sandboxes
🧯 If You Can't Patch
- Implement strict input validation for PDF files
- Deploy memory protection mechanisms like ASLR and DEP
🔍 How to Verify
Check if Vulnerable:
Check MuPDF version with 'mupdf --version' or examine application dependenciesCheck Version:
mupdf --versionVerify Fix Applied:
Verify MuPDF version is newer than 1.17.0-rc1 or includes commit 96751b25462f83d6e16a9afaf8980b0c3f979c8b📡 Detection & Monitoring
Log Indicators:
- Application crashes when processing PDF files
- Memory access violation errors
Network Indicators:
- Unusual PDF file uploads to web services
SIEM Query:
source="application.log" AND ("segmentation fault" OR "access violation") AND "pdf"