CVE-2020-21833
📋 TL;DR
CVE-2020-21833 is a heap-based buffer overflow vulnerability in GNU LibreDWG's DWG file parser. Attackers can exploit this by crafting malicious DWG files to potentially execute arbitrary code or cause denial of service. This affects any application or service that uses LibreDWG to process 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 full system compromise.
Likely Case
Application crash (denial of service) when processing malicious DWG files, with potential for limited code execution in some scenarios.
If Mitigated
Application crash without code execution if memory protections like ASLR are effective.
🎯 Exploit Status
Exploitation requires the victim to process a malicious DWG file. The GitHub issue contains technical details that could aid exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 0.10.1 or later
Vendor Advisory: https://github.com/LibreDWG/libredwg/issues/188
Restart Required: No
Instructions:
1. Update LibreDWG to version 0.10.1 or later. 2. Recompile any applications using LibreDWG with the updated library. 3. Replace the vulnerable library in deployment environments.
🔧 Temporary Workarounds
Input validation for DWG files
allImplement strict validation of DWG files before processing with LibreDWG
Sandbox LibreDWG processing
linuxRun LibreDWG in a container or sandbox with limited privileges
docker run --read-only --cap-drop=ALL -v /tmp:/tmp:ro your_app
🧯 If You Can't Patch
- Disable LibreDWG processing of untrusted DWG files from external sources
- Implement network segmentation to isolate systems using vulnerable LibreDWG versions
🔍 How to Verify
Check if Vulnerable:
Check if LibreDWG version is 0.10 or earlier: `libredwg --version` or check linked library versionCheck Version:
libredwg --versionVerify Fix Applied:
Verify LibreDWG version is 0.10.1 or later: `libredwg --version | grep -q '0.10.1' && echo 'Patched'`📡 Detection & Monitoring
Log Indicators:
- Application crashes when processing DWG files
- Memory access violation errors in application logs
Network Indicators:
- Unusual DWG file uploads to web applications
- Multiple failed parsing attempts
SIEM Query:
source="application.log" AND ("segmentation fault" OR "buffer overflow" OR "access violation") AND "dwg"