CVE-2021-39818
📋 TL;DR
Adobe InCopy versions 11.1 and earlier contain a memory corruption vulnerability when processing malicious TIFF files. This could allow attackers to execute arbitrary code with the privileges of the current user. Exploitation requires user interaction, such as opening a specially crafted file.
💻 Affected Systems
- Adobe InCopy
📦 What is this software?
Incopy by Adobe
Incopy by Adobe
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via arbitrary code execution with user privileges, potentially leading to data theft, ransomware deployment, or lateral movement.
Likely Case
Local privilege escalation or malware installation when a user opens a malicious TIFF file, resulting in compromised user accounts and data loss.
If Mitigated
Limited impact due to patched systems, application sandboxing, or restricted user permissions preventing full system compromise.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious file). No public exploit code has been disclosed as of knowledge cutoff.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.1.1 or later
Vendor Advisory: https://helpx.adobe.com/security/products/incopy/apsb21-71.html
Restart Required: Yes
Instructions:
1. Open Adobe InCopy. 2. Go to Help > Updates. 3. Follow prompts to install available updates. 4. Alternatively, download and install the latest version from Adobe's website. 5. Restart the application after installation.
🔧 Temporary Workarounds
Disable TIFF file association
allPrevent InCopy from automatically opening TIFF files by changing file associations
Windows: Control Panel > Default Programs > Associate a file type or protocol with a program
macOS: Right-click TIFF file > Get Info > Open With > Change
Application sandboxing
allRun InCopy in restricted environments to limit potential damage
Windows: Use AppLocker or Windows Sandbox
macOS: Use sandbox-exec or create restricted user account
🧯 If You Can't Patch
- Implement strict file handling policies to block TIFF files from untrusted sources
- Use application control solutions to restrict InCopy execution to trusted directories only
🔍 How to Verify
Check if Vulnerable:
Check InCopy version via Help > About InCopy. If version is 11.1 or earlier, system is vulnerable.Check Version:
Windows: wmic product where name="Adobe InCopy" get version
macOS: /Applications/Adobe\ InCopy\ */Adobe\ InCopy.app/Contents/Info.plist | grep -A1 CFBundleShortVersionStringVerify Fix Applied:
Verify version is 11.1.1 or later in Help > About InCopy. Test opening known safe TIFF files to ensure functionality.📡 Detection & Monitoring
Log Indicators:
- Application crashes with memory access violations
- Unexpected child processes spawned from InCopy
- TIFF file processing errors in application logs
Network Indicators:
- Unusual outbound connections from InCopy process
- File downloads from untrusted sources followed by InCopy execution
SIEM Query:
process_name:"incopy.exe" AND (event_id:1000 OR event_id:1001) OR file_extension:".tif" AND process_name:"incopy.exe"