CVE-2021-41456
📋 TL;DR
A stack buffer overflow vulnerability in MP4Box v1.0.1 allows attackers to cause denial of service by exploiting improper bounds checking in the nhmldmx_send_sample() function. This affects systems running GPAC's MP4Box multimedia processing tool. Attackers can crash the application by providing specially crafted input.
💻 Affected Systems
- GPAC MP4Box
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if combined with other vulnerabilities or memory corruption techniques.
Likely Case
Application crash and denial of service, disrupting multimedia processing operations.
If Mitigated
Limited impact with proper input validation and memory protection mechanisms in place.
🎯 Exploit Status
The vulnerability is in a core parsing function and can be triggered by processing malicious media files.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: GPAC versions after the fix in GitHub commit addressing the issue
Vendor Advisory: https://github.com/gpac/gpac/issues/1911
Restart Required: Yes
Instructions:
1. Update GPAC to the latest version from the official repository. 2. Recompile MP4Box if using source. 3. Restart any services using MP4Box.
🔧 Temporary Workarounds
Input Validation Filter
allImplement strict input validation for media files before processing with MP4Box
# Example: Use file command to verify file types before processing
file --mime-type input.mp4 | grep -q 'video/mp4' && mp4box ...
Memory Protection
linuxEnable stack protection and address space layout randomization
# Linux: Ensure ASLR is enabled
sysctl -w kernel.randomize_va_space=2
# Compile with stack protection: -fstack-protector-all
🧯 If You Can't Patch
- Isolate MP4Box usage to dedicated, non-critical systems with limited network access
- Implement strict file upload controls and sandbox MP4Box execution
🔍 How to Verify
Check if Vulnerable:
Check MP4Box version: mp4box -version | grep -i versionCheck Version:
mp4box -versionVerify Fix Applied:
Verify version is updated and test with known safe media files📡 Detection & Monitoring
Log Indicators:
- Segmentation fault errors in system logs
- MP4Box process crashes
- Abnormal termination of media processing jobs
Network Indicators:
- Unusual file uploads to media processing systems
- Repeated connection attempts to MP4Box services
SIEM Query:
process_name:"mp4box" AND (event_type:"crash" OR exit_code:139)