CVE-2020-21814
📋 TL;DR
CVE-2020-21814 is a heap-based buffer overflow vulnerability in GNU LibreDWG's htmlwescape function that allows attackers to execute arbitrary code or cause denial of service. This affects systems using LibreDWG to process DWG files, particularly CAD software and document conversion tools. The vulnerability is exploitable when processing specially crafted DWG files.
💻 Affected Systems
- GNU LibreDWG
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the LibreDWG process, potentially leading to complete system compromise.
Likely Case
Application crash (denial of service) when processing malicious DWG files, with potential for code execution in certain configurations.
If Mitigated
Application crash without code execution if memory protections like ASLR are effective.
🎯 Exploit Status
Proof of concept exists in GitHub issue #182. Exploitation requires crafting a malicious DWG file that triggers the buffer overflow in htmlwescape function.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.10.2642 and later
Vendor Advisory: https://github.com/LibreDWG/libredwg/issues/182
Restart Required: Yes
Instructions:
1. Update LibreDWG to version 0.10.2642 or later. 2. Rebuild any applications using LibreDWG library. 3. Restart affected services or applications.
🔧 Temporary Workarounds
Disable DWG file processing
allTemporarily disable LibreDWG-based DWG file processing in applications
# Configure applications to reject DWG files or use alternative converters
Input validation
allImplement strict validation of DWG files before processing with LibreDWG
# Add file type verification and size limits in application code
🧯 If You Can't Patch
- Isolate LibreDWG applications in restricted network segments
- Implement application allowlisting to prevent unauthorized LibreDWG execution
🔍 How to Verify
Check if Vulnerable:
Check LibreDWG version: libredwg --version or check package manager. If version is 0.10.2641 or earlier, system is vulnerable.Check Version:
libredwg --version 2>/dev/null || dpkg -l | grep libredwg || rpm -qa | grep libredwgVerify Fix Applied:
Verify LibreDWG version is 0.10.2642 or later. Test with known safe DWG files to ensure functionality.📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults in LibreDWG processes
- Memory access violation errors in application logs
Network Indicators:
- Unusual DWG file uploads to web applications
- Large or malformed DWG file transfers
SIEM Query:
process_name:"libredwg" AND (event_type:"crash" OR exit_code:139)