CVE-2021-40759
📋 TL;DR
Adobe After Effects versions 18.4.1 and earlier contain a memory corruption vulnerability when processing malicious .m4a files. This could allow attackers to execute arbitrary code with the privileges of the current user. Users who open specially crafted .m4a files are affected.
💻 Affected Systems
- Adobe After Effects
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via arbitrary code execution leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Local privilege escalation leading to user account compromise and potential lateral movement within the network.
If Mitigated
Limited impact due to user account restrictions, potentially only affecting local files and settings.
🎯 Exploit Status
Requires user interaction to open malicious file. Memory corruption vulnerabilities typically require some exploit development skill.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 18.4.2 or later
Vendor Advisory: https://helpx.adobe.com/security/products/after_effects/apsb21-79.html
Restart Required: Yes
Instructions:
1. Open Adobe Creative Cloud application. 2. Navigate to 'Apps' tab. 3. Find Adobe After Effects. 4. Click 'Update' button. 5. Restart After Effects after update completes.
🔧 Temporary Workarounds
Block .m4a file processing
allPrevent After Effects from opening .m4a files by modifying file associations or using application control policies.
Restrict file execution
allUse application whitelisting to prevent execution of untrusted .m4a files in After Effects.
🧯 If You Can't Patch
- Implement strict user training about opening untrusted media files
- Deploy endpoint detection and response (EDR) to monitor for suspicious After Effects behavior
🔍 How to Verify
Check if Vulnerable:
Check After Effects version via Help > About After Effects. If version is 18.4.1 or earlier, system is vulnerable.Check Version:
On Windows: wmic product where name="Adobe After Effects" get version
On macOS: /Applications/Adobe\ After\ Effects\ */Adobe\ After\ Effects.app/Contents/Info.plist | grep -A1 CFBundleShortVersionStringVerify Fix Applied:
Verify After Effects version is 18.4.2 or later via Help > About After Effects.📡 Detection & Monitoring
Log Indicators:
- After Effects crash logs with .m4a file references
- Unexpected process spawning from After Effects
Network Indicators:
- Unusual outbound connections from After Effects process
SIEM Query:
process_name:"AfterFX.exe" AND (file_extension:".m4a" OR process_crash:true)