CVE-2021-21858
📋 TL;DR
CVE-2021-21858 is an integer overflow vulnerability in GPAC's MPEG-4 decoder that can lead to heap-based buffer overflow and memory corruption when processing malicious video files. Attackers can exploit this by tricking users into opening specially crafted MPEG-4 videos. This affects applications using the GPAC library for multimedia processing.
💻 Affected Systems
- GPAC Project on Advanced Content library
- Applications using GPAC library for MPEG-4 decoding
📦 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 in the context of the vulnerable application.
If Mitigated
Application crash with no further impact if memory protections (ASLR, DEP) are effective.
🎯 Exploit Status
Exploitation requires user interaction to open malicious video file. Proof-of-concept code is publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: GPAC 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/applications.
🔧 Temporary Workarounds
Disable MPEG-4 processing
allConfigure applications to disable MPEG-4 video decoding if not required
Application sandboxing
allRun vulnerable applications in restricted environments/sandboxes
🧯 If You Can't Patch
- Implement strict file upload controls and scanning for MPEG-4 files
- Use application allowlisting to prevent execution of untrusted multimedia applications
🔍 How to Verify
Check if Vulnerable:
Check GPAC library version: gpac -version or examine linked library versions in applicationsCheck Version:
gpac -version 2>/dev/null | head -1Verify Fix Applied:
Verify GPAC version is 1.0.2 or higher and applications have been rebuilt with updated library📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults when processing video files
- Unexpected process termination in multimedia applications
Network Indicators:
- Unusual MPEG-4 file downloads to endpoints
- Video file transfers to multimedia processing servers
SIEM Query:
Process:Terminated AND (ImagePath:*gpac* OR CommandLine:*mp4*)