CVE-2021-21010
📋 TL;DR
CVE-2021-21010 is an uncontrolled search path vulnerability in Adobe InCopy for Windows that allows arbitrary code execution when a user opens a malicious file. This affects InCopy version 15.1.1 and earlier on Windows systems. Attackers can exploit this to run malicious code with the privileges of the current user.
💻 Affected Systems
- Adobe InCopy
📦 What is this software?
Incopy by Adobe
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining the same privileges as the logged-in user, potentially leading to data theft, ransomware deployment, or lateral movement.
Likely Case
Malware installation or data exfiltration from the compromised user account.
If Mitigated
No impact if users don't open untrusted files and proper application whitelisting is enforced.
🎯 Exploit Status
Exploitation requires user interaction but is technically simple once malicious file is opened.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 15.1.2 or later
Vendor Advisory: https://helpx.adobe.com/security/products/incopy/apsb21-05.html
Restart Required: Yes
Instructions:
1. Open Adobe InCopy. 2. Go to Help > Updates. 3. Install available updates to version 15.1.2 or later. 4. Restart the application.
🔧 Temporary Workarounds
Restrict file execution from untrusted locations
windowsConfigure Windows to prevent execution of files from temporary directories and untrusted network locations.
Use Windows AppLocker or Software Restriction Policies to block execution from %TEMP%, %APPDATA%, and network shares
Disable DLL search path hijacking
windowsSet SafeDllSearchMode registry key to prevent DLL search order vulnerabilities.
reg add "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager" /v SafeDllSearchMode /t REG_DWORD /d 1 /f
🧯 If You Can't Patch
- Implement application whitelisting to prevent unauthorized executables from running
- Educate users not to open files from untrusted sources and disable macros/scripts in documents
🔍 How to Verify
Check if Vulnerable:
Check InCopy version via Help > About InCopy. If version is 15.1.1 or earlier, system is vulnerable.Check Version:
Not applicable - check via application GUIVerify Fix Applied:
Verify version is 15.1.2 or later in Help > About InCopy.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing InCopy process spawning unexpected child processes
- DLL loading from unusual locations like %TEMP%
Network Indicators:
- Unexpected outbound connections from InCopy process
SIEM Query:
Process Creation where Parent Process Name contains "InCopy" AND (Process Name contains "cmd" OR Process Name contains "powershell" OR Process Name contains "wscript")