CVE-2021-21090
📋 TL;DR
CVE-2021-21090 is a path traversal vulnerability in Adobe InCopy that allows remote code execution when a user opens a malicious file. Attackers can exploit this to execute arbitrary code with the victim's privileges. All users of Adobe InCopy version 16.0 and earlier are affected.
💻 Affected Systems
- Adobe InCopy
📦 What is this software?
Incopy by Adobe
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control of the victim's computer, data theft, ransomware deployment, and lateral movement within the network.
Likely Case
Malware installation leading to data exfiltration, credential theft, or system disruption for individual users who open malicious files.
If Mitigated
Limited impact with proper security controls, potentially isolated to the application sandbox or blocked by endpoint protection.
🎯 Exploit Status
Exploitation requires social engineering to get users to open malicious files. No authentication is required once the file is opened.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 16.1 and later
Vendor Advisory: https://helpx.adobe.com/security/products/incopy/apsb21-25.html
Restart Required: Yes
Instructions:
1. Open Adobe InCopy. 2. Go to Help > Check for Updates. 3. Follow prompts to install version 16.1 or later. 4. Restart the application.
🔧 Temporary Workarounds
Disable automatic file opening
allConfigure system to not automatically open downloaded files and require explicit user action.
Application sandboxing
allRun Adobe InCopy in a sandboxed environment to limit potential damage from exploitation.
🧯 If You Can't Patch
- Implement application whitelisting to block execution of unauthorized applications
- Deploy endpoint detection and response (EDR) solutions to detect and block malicious file execution
🔍 How to Verify
Check if Vulnerable:
Check Adobe InCopy version in Help > About Adobe InCopy. If version is 16.0 or earlier, the system is vulnerable.Check Version:
On Windows: wmic product where name="Adobe InCopy" get version
On macOS: /Applications/Adobe\ InCopy/Adobe\ InCopy.app/Contents/Info.plistVerify Fix Applied:
Verify version is 16.1 or later in Help > About Adobe InCopy.📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns from Adobe InCopy
- Process creation from Adobe InCopy with suspicious parameters
Network Indicators:
- Outbound connections from Adobe InCopy to unknown IPs
- DNS requests for suspicious domains from Adobe InCopy process
SIEM Query:
process_name:"Adobe InCopy.exe" AND (process_args:"*../*" OR process_args:"*..\\*")