CVE-2021-38092
📋 TL;DR
This integer overflow vulnerability in FFmpeg's convolution filter 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 that process untrusted video content. Media processing servers, video conversion services, and applications embedding FFmpeg are particularly vulnerable.
💻 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 enables memory corruption that can be weaponized.
Likely Case
Denial of service through application crash when processing malicious video files, disrupting media processing services.
If Mitigated
Limited impact with proper input validation and sandboxing, potentially causing only application crashes without privilege escalation.
🎯 Exploit Status
Exploitation requires crafting a malicious video file that triggers the integer overflow in the convolution filter. No public proof-of-concept has been released, but the vulnerability is well-documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit 99f8d32129dd233d4eb2efa44678a0bc44869f23 and later versions
Vendor Advisory: https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/99f8d32129dd233d4eb2efa44678a0bc44869f23
Restart Required: Yes
Instructions:
1. Update FFmpeg to version 4.4 or later. 2. Alternatively, apply the specific patch from commit 99f8d32129dd233d4eb2efa44678a0bc44869f23. 3. Recompile FFmpeg if building from source. 4. Restart any services using FFmpeg.
🔧 Temporary Workarounds
Disable convolution filter
allPrevent use of the vulnerable filter_prewitt function by disabling convolution filter operations
ffmpeg -filter_complex 'convolution=disable' input.mp4 output.mp4
Sandbox FFmpeg processing
linuxRun FFmpeg in a container or sandbox with limited privileges to contain potential exploitation
docker run --security-opt no-new-privileges -v /input:/input -v /output:/output ffmpeg ffmpeg -i /input/video.mp4 /output/processed.mp4
🧯 If You Can't Patch
- Implement strict input validation - only allow trusted video sources and validate file formats before processing
- Deploy network segmentation - isolate FFmpeg processing systems from critical infrastructure
🔍 How to Verify
Check if Vulnerable:
Check FFmpeg version: ffmpeg -version | grep 'version' and verify if it's 4.2.1. Also check if the system processes video files from untrusted sources.Check Version:
ffmpeg -version | grep 'version'Verify Fix Applied:
Verify FFmpeg version is 4.4 or later, or check if commit 99f8d32129dd233d4eb2efa44678a0bc44869f23 is included in your build.📡 Detection & Monitoring
Log Indicators:
- FFmpeg process crashes with segmentation faults
- Unexpected termination of media processing services
- Error logs mentioning convolution.c or filter_prewitt
Network Indicators:
- Unusual video file uploads to media processing endpoints
- Multiple failed media processing requests
SIEM Query:
source="ffmpeg.log" AND ("segmentation fault" OR "SIGSEGV" OR "convolution")