CVE-2021-21847
📋 TL;DR
This vulnerability allows remote code execution through a heap-based buffer overflow in GPAC's MPEG-4 decoder. Attackers can exploit it by tricking users into opening malicious video files. Systems using GPAC v1.0.1 for video processing are affected.
💻 Affected Systems
- GPAC Project on Advanced Content library
📦 What is this software?
Gpac by Gpac
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with arbitrary code execution leading to complete data loss, lateral movement, and persistent backdoor installation.
Likely Case
Application crash leading to denial of service, with potential for limited code execution in the context of the video processing application.
If Mitigated
Application crash without code execution if memory protections like ASLR/DEP are properly implemented and effective.
🎯 Exploit Status
Exploitation requires user interaction to open malicious video file. The vulnerability is in the 'stts' atom decoder within MPEG-4 parsing functionality.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v1.0.2 or later
Vendor Advisory: https://github.com/gpac/gpac/security/advisories
Restart Required: Yes
Instructions:
1. Update GPAC library to version 1.0.2 or later. 2. Rebuild any applications using GPAC. 3. Restart affected services or applications.
🔧 Temporary Workarounds
Disable MPEG-4 processing
allConfigure applications to disable MPEG-4 video decoding if not required
Input validation
allImplement strict file type validation and size limits for video uploads
🧯 If You Can't Patch
- Implement application sandboxing to limit impact of potential exploitation
- Deploy endpoint detection and response (EDR) solutions to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check GPAC library version: gpac -version or examine linked library version in applicationsCheck Version:
gpac -version 2>&1 | grep -i versionVerify Fix Applied:
Confirm GPAC version is 1.0.2 or higher and verify applications have been rebuilt with updated library📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults in video processing
- Unusual memory allocation patterns in video decoding processes
Network Indicators:
- Unexpected video file downloads to systems running GPAC
- MPEG-4 files with unusual structure or size
SIEM Query:
process_name:"gpac" AND (event_type:crash OR memory_usage:anomalous)🔗 References
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1297
- https://www.debian.org/security/2021/dsa-4966
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2021-1297
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1297
- https://www.debian.org/security/2021/dsa-4966
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2021-1297
