CVE-2020-21816
📋 TL;DR
CVE-2020-21816 is a heap-based buffer overflow vulnerability in GNU LibreDWG's HTML escape function that allows attackers to execute arbitrary code or cause denial of service. This affects applications that process untrusted DWG files using vulnerable LibreDWG versions. Users and systems that handle CAD files from untrusted sources are at risk.
💻 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, disrupting CAD file processing workflows.
If Mitigated
Limited impact if proper input validation and memory protections are in place, potentially just application instability.
🎯 Exploit Status
Exploitation requires crafting a malicious DWG file that triggers the buffer overflow when processed. The GitHub issue contains technical details that could aid exploitation.
🛠️ 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. 3. Restart affected services.
🔧 Temporary Workarounds
Disable DWG file processing
allTemporarily disable LibreDWG-based DWG file processing until patched.
# Disable services using LibreDWG
sudo systemctl stop [service-name]
Input validation
allImplement strict validation of DWG files before processing with LibreDWG.
🧯 If You Can't Patch
- Isolate systems using LibreDWG from untrusted networks
- Implement application whitelisting to prevent execution of malicious payloads
🔍 How to Verify
Check if Vulnerable:
Check LibreDWG version: redwg --version or check installed package version.Check Version:
redwg --versionVerify Fix Applied:
Verify version is 0.10.2642 or later and test with sample DWG files.📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults
- Memory access violation errors in logs
- Unexpected process termination
Network Indicators:
- Unusual outbound connections from LibreDWG processes
- Large file uploads to DWG processing endpoints
SIEM Query:
process_name:"redwg" AND (event_type:"crash" OR exit_code:139)