CVE-2021-38094
📋 TL;DR
This integer overflow vulnerability in FFmpeg's filter_sobel function allows attackers to cause denial of service or potentially execute arbitrary code by processing specially crafted video files. It affects systems running FFmpeg 4.2.1 and potentially other versions that haven't been patched. Users who process untrusted video content with FFmpeg are at risk.
💻 Affected Systems
- FFmpeg
📦 What is this software?
Ffmpeg by Ffmpeg
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if the integer overflow can be leveraged for memory corruption attacks.
Likely Case
Denial of service through application crash when processing malicious video files.
If Mitigated
Limited to denial of service if proper input validation and sandboxing are implemented.
🎯 Exploit Status
Exploitation requires crafting malicious video files that trigger the integer overflow when processed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit 99f8d32129dd233d4eb2efa44678a0bc44869f23
Vendor Advisory: https://trac.ffmpeg.org/ticket/8263
Restart Required: No
Instructions:
1. Update FFmpeg to version containing commit 99f8d32129dd233d4eb2efa44678a0bc44869f23
2. Recompile if using source distribution
3. Restart any services using FFmpeg
🔧 Temporary Workarounds
Disable convolution filter
allPrevent use of the vulnerable filter_sobel function
# Configure FFmpeg to avoid using convolution filters with sobel operator
Input validation
allImplement strict input validation for video files before processing
# Use file validation tools before passing to FFmpeg
🧯 If You Can't Patch
- Isolate FFmpeg processing to dedicated, restricted containers or VMs
- Implement strict file upload controls and only process trusted video content
🔍 How to Verify
Check if Vulnerable:
Check FFmpeg version and verify if it contains the vulnerable commitCheck Version:
ffmpeg -versionVerify Fix Applied:
Verify FFmpeg version includes commit 99f8d32129dd233d4eb2efa44678a0bc44869f23📡 Detection & Monitoring
Log Indicators:
- FFmpeg segmentation faults
- Unexpected process termination when processing video files
Network Indicators:
- Unusual video file uploads to processing systems
SIEM Query:
Process:ffmpeg AND (EventID:1000 OR Signal:SIGSEGV)