CVE-2021-44701
📋 TL;DR
CVE-2021-44701 is a use-after-free vulnerability in Adobe Acrobat Reader DC that could allow arbitrary code execution when processing malicious PDF files. Attackers can exploit this by tricking users into opening specially crafted PDF documents. Users of Adobe Acrobat Reader DC versions 21.007.20099 and earlier, 20.004.30017 and earlier, and 17.011.30204 and earlier are affected.
💻 Affected Systems
- Adobe Acrobat Reader DC
📦 What is this software?
Acrobat by Adobe
Acrobat by Adobe
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining the same privileges as the current user, potentially leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Limited code execution in user context leading to credential theft, data exfiltration, or installation of additional malware.
If Mitigated
No impact if proper patching and security controls are implemented, including application whitelisting and user education.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious PDF). No public exploit code available at disclosure time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 21.007.20099 (Continuous Track), 20.004.30017 (Classic 2020 Track), 17.011.30204 (Classic 2017 Track) and later versions
Vendor Advisory: https://helpx.adobe.com/security/products/acrobat/apsb22-01.html
Restart Required: Yes
Instructions:
1. Open Adobe Acrobat Reader DC. 2. Go to Help > Check for Updates. 3. Follow prompts to install available updates. 4. Restart the application when prompted.
🔧 Temporary Workarounds
Disable JavaScript in Adobe Reader
allPrevents exploitation by disabling JavaScript execution which may be required for the vulnerability
Edit > Preferences > JavaScript > Uncheck 'Enable Acrobat JavaScript'
Use Protected View
allOpen PDFs in Protected View mode to prevent automatic script execution
File > Open > Select 'Protected View' option when opening files
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized PDF readers
- Deploy email filtering to block malicious PDF attachments and educate users about phishing risks
🔍 How to Verify
Check if Vulnerable:
Check Adobe Reader version via Help > About Adobe Acrobat Reader DC and compare with affected versionsCheck Version:
Windows: wmic product where name="Adobe Acrobat Reader DC" get version
macOS: /Applications/Adobe\ Acrobat\ Reader\ DC.app/Contents/Info.plist | grep -A1 CFBundleShortVersionStringVerify Fix Applied:
Verify version is updated to 21.007.20099 or later (Continuous), 20.004.30017 or later (Classic 2020), or 17.011.30204 or later (Classic 2017)📡 Detection & Monitoring
Log Indicators:
- Adobe Reader crash logs with exception codes
- Windows Event Logs showing unexpected process creation from AcroRd32.exe
Network Indicators:
- Unexpected outbound connections from Adobe Reader process
- DNS requests to suspicious domains after PDF opening
SIEM Query:
process_name:"AcroRd32.exe" AND (event_id:1 OR parent_process_name:"explorer.exe") AND command_line:"*.pdf"