CVE-2021-21100
📋 TL;DR
Adobe Digital Editions versions 4.5.11.187245 and earlier contain a privilege escalation vulnerability during installation that allows an unauthenticated attacker to write arbitrary files to the system with the current user's permissions. This affects users who install or update Adobe Digital Editions on their systems. Exploitation requires user interaction through opening a malicious file.
💻 Affected Systems
- Adobe Digital Editions
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An attacker could achieve full system compromise by writing malicious executables to startup locations, installing backdoors, or overwriting critical system files, leading to persistent access and data theft.
Likely Case
Attackers would likely use this to install malware, ransomware, or credential stealers on the victim's system, potentially leading to data exfiltration or system encryption.
If Mitigated
With proper user awareness training and limited user privileges, the impact would be contained to the user's profile and data rather than full system compromise.
🎯 Exploit Status
Exploitation requires user interaction (opening a malicious file) and knowledge of the installation process. No public exploit code has been identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.5.12 and later
Vendor Advisory: https://helpx.adobe.com/security/products/Digital-Editions/apsb21-26.html
Restart Required: Yes
Instructions:
1. Open Adobe Digital Editions. 2. Go to Help > Check for Updates. 3. Follow prompts to install version 4.5.12 or later. 4. Restart the application and system if prompted.
🔧 Temporary Workarounds
Disable automatic updates
allPrevent automatic installation of Adobe Digital Editions updates which could trigger the vulnerability
Run with limited privileges
windowsInstall and run Adobe Digital Editions with a standard user account rather than administrator privileges
🧯 If You Can't Patch
- Uninstall Adobe Digital Editions if not required for business operations
- Implement application whitelisting to prevent unauthorized installations
- Educate users about the risks of opening untrusted files
- Monitor for suspicious file writes during installation processes
🔍 How to Verify
Check if Vulnerable:
Check Adobe Digital Editions version in Help > About. If version is 4.5.11.187245 or earlier, the system is vulnerable.Check Version:
On Windows: Check registry at HKEY_LOCAL_MACHINE\SOFTWARE\Adobe\Digital Editions\Version or check Help > About in the applicationVerify Fix Applied:
Verify version is 4.5.12 or later in Help > About. Test installation process with controlled files to ensure no unauthorized writes occur.📡 Detection & Monitoring
Log Indicators:
- Unexpected file writes during Adobe Digital Editions installation
- Suspicious process creation during installation
- Failed installation attempts with error codes
Network Indicators:
- Downloads from unusual sources during update process
- Connections to non-Adobe update servers
SIEM Query:
Process creation where parent process contains 'DigitalEditions' AND (file write operations to sensitive locations OR network connections to non-standard update endpoints)