CVE-2021-31254
📋 TL;DR
CVE-2021-31254 is a buffer overflow vulnerability in GPAC's MP4Box tool that allows attackers to cause denial of service or execute arbitrary code by providing a specially crafted MP4 file with invalid IV sizes. This affects systems running vulnerable versions of GPAC that process untrusted media files. The vulnerability is particularly dangerous for media processing servers and applications that use GPAC libraries.
💻 Affected Systems
- GPAC
- MP4Box
📦 What is this software?
Gpac by Gpac
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the GPAC process, potentially leading to full system compromise.
Likely Case
Denial of service through application crashes when processing malicious media files.
If Mitigated
Limited impact if proper input validation and sandboxing are implemented.
🎯 Exploit Status
Exploitation requires providing a malicious MP4 file to the vulnerable application. The GitHub issues show proof-of-concept discussions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: GPAC versions after commit 8986422c21fbd9a7bf6561cae65aae42077447e8
Vendor Advisory: https://github.com/gpac/gpac/commit/8986422c21fbd9a7bf6561cae65aae42077447e8
Restart Required: Yes
Instructions:
1. Update GPAC to latest version. 2. Rebuild applications using GPAC libraries. 3. Restart affected services.
🔧 Temporary Workarounds
Disable MP4 processing
allTemporarily disable MP4 file processing in applications using GPAC
Input validation
allImplement strict file type validation before passing to GPAC
🧯 If You Can't Patch
- Implement network segmentation to isolate GPAC processing systems
- Use application sandboxing/containerization to limit exploit impact
🔍 How to Verify
Check if Vulnerable:
Check GPAC version with 'MP4Box -version' or 'gpac -version'. If version is 1.0.1 or earlier, system is vulnerable.Check Version:
MP4Box -version 2>&1 | head -1Verify Fix Applied:
Verify GPAC version is newer than commit 8986422c21fbd9a7bf6561cae65aae42077447e8. Test with known malicious MP4 files.📡 Detection & Monitoring
Log Indicators:
- GPAC/MP4Box crash logs
- Segmentation fault errors in system logs
- Abnormal process termination
Network Indicators:
- Unusual MP4 file uploads to media processing endpoints
- Large number of failed media processing requests
SIEM Query:
process_name:"MP4Box" AND (event_type:crash OR exit_code:139)