CVE-2021-21854
📋 TL;DR
This vulnerability allows attackers to execute arbitrary code or cause denial of service by tricking users into opening specially crafted MPEG-4 video files. It affects applications using the GPAC library for media processing, potentially impacting media players, streaming applications, and video processing tools.
💻 Affected Systems
- GPAC Project on Advanced Content library
- Applications using GPAC library
- Debian packages with vulnerable GPAC
📦 What is this software?
Gpac by Gpac
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Application crash (denial of service) or limited code execution within the application context.
If Mitigated
Application crash with no further impact if proper sandboxing and privilege separation are implemented.
🎯 Exploit Status
Exploitation requires user interaction (opening a malicious file). The vulnerability is in a widely used media library, making it attractive for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: GPAC v1.0.2 or later
Vendor Advisory: https://github.com/gpac/gpac/issues/1766
Restart Required: Yes
Instructions:
1. Update GPAC library to version 1.0.2 or later. 2. Rebuild or update any applications using GPAC. 3. Restart affected applications or services.
🔧 Temporary Workarounds
Disable MPEG-4 processing
allConfigure applications to disable MPEG-4 file processing if not required
Application sandboxing
allRun vulnerable applications in sandboxed environments with limited privileges
🧯 If You Can't Patch
- Implement strict file type validation to block untrusted MPEG-4 files
- Use application allowlisting to prevent execution of unknown media processing applications
🔍 How to Verify
Check if Vulnerable:
Check GPAC library version: gpac -version or check package version in your distributionCheck Version:
gpac -version 2>/dev/null | head -1Verify Fix Applied:
Verify GPAC version is 1.0.2 or later and test with known safe MPEG-4 files📡 Detection & Monitoring
Log Indicators:
- Application crashes when processing MPEG-4 files
- Memory access violation errors in application logs
Network Indicators:
- Unusual outbound connections from media applications
- MPEG-4 file downloads from untrusted sources
SIEM Query:
source="application_logs" AND ("segmentation fault" OR "access violation" OR "heap corruption") AND process="*gpac*" OR process="*media*"