CVE-2021-21835
📋 TL;DR
This vulnerability allows remote code execution through a specially crafted MPEG-4 video file. Attackers can exploit it by tricking users into opening malicious videos, potentially taking full control of affected systems. The GPAC multimedia framework/library is affected when processing MPEG-4 content.
💻 Affected Systems
- GPAC Project on Advanced Content library
📦 What is this software?
Gpac by Gpac
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with remote code execution, allowing attackers to install malware, steal data, or create persistent backdoors.
Likely Case
Application crash leading to denial of service, with potential for remote code execution if exploit is weaponized.
If Mitigated
Limited to application crash if exploit fails or memory protections are in place.
🎯 Exploit Status
Exploit requires user interaction to open malicious video file. Proof-of-concept available in Talos advisory.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v1.0.2 or later
Vendor Advisory: https://github.com/gpac/gpac/security/advisories/GHSA-5x5h-9wrq-2c4h
Restart Required: Yes
Instructions:
1. Update GPAC to version 1.0.2 or later. 2. Rebuild any applications using GPAC library. 3. Restart affected services/applications.
🔧 Temporary Workarounds
Disable MPEG-4 processing
allConfigure applications to avoid processing MPEG-4 files with GPAC library
Application-specific configuration required
Input validation
allImplement file type validation before passing to GPAC decoder
Implement file signature checking in application code
🧯 If You Can't Patch
- Implement application sandboxing to limit impact of potential exploitation
- Use endpoint protection with memory corruption detection capabilities
🔍 How to Verify
Check if Vulnerable:
Check GPAC library version: gpac -version or examine linked library version in applicationsCheck Version:
gpac -versionVerify Fix Applied:
Confirm GPAC version is 1.0.2 or higher: gpac -version | grep -E '1\.0\.[2-9]|1\.[1-9]'📡 Detection & Monitoring
Log Indicators:
- Application crashes with GPAC/MP4Box processes
- Memory access violation errors in application logs
Network Indicators:
- Unusual outbound connections after video file processing
- Download of suspicious video files
SIEM Query:
process:gpac OR process:MP4Box AND (event_id:1000 OR exception_code:c0000005)