CVE-2021-21062
📋 TL;DR
A memory corruption vulnerability in Adobe Acrobat Reader DC allows arbitrary code execution when parsing malicious PDF files. Attackers can exploit this by tricking users into opening specially crafted PDFs, potentially gaining full control of the affected system. This affects users running vulnerable versions of Acrobat Reader DC across multiple release tracks.
💻 Affected Systems
- Adobe Acrobat Reader DC
📦 What is this software?
Acrobat by Adobe
Acrobat by Adobe
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining the same privileges as the logged-in user, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Malicious actors using phishing emails with booby-trapped PDF attachments to compromise individual workstations, then moving laterally within networks.
If Mitigated
Limited impact with proper application whitelisting, network segmentation, and user training preventing successful exploitation.
🎯 Exploit Status
Exploitation requires user interaction but is straightforward once malicious PDF is opened. Memory corruption vulnerabilities in PDF parsers are commonly weaponized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2020.013.20075, 2020.001.30019, 2017.011.30189 or later
Vendor Advisory: https://helpx.adobe.com/security/products/acrobat/apsb21-09.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 JavaScript-based exploitation vectors that might accompany memory corruption
Edit > Preferences > JavaScript > Uncheck 'Enable JavaScript'
Use Protected View
allForce all PDFs to open in Protected View to limit potential damage
Edit > Preferences > Security (Enhanced) > Check 'Enable Protected View at startup'
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized PDF readers
- Deploy network segmentation to limit lateral movement from compromised endpoints
🔍 How to Verify
Check if Vulnerable:
Check Help > About Adobe Acrobat Reader DC and compare version against affected rangesCheck Version:
On Windows: wmic product where name="Adobe Acrobat Reader DC" get versionVerify Fix Applied:
Verify version is 2020.013.20075+, 2020.001.30019+, or 2017.011.30189+📡 Detection & Monitoring
Log Indicators:
- Unexpected process crashes of AcroRd32.exe
- Suspicious child processes spawned from AcroRd32.exe
Network Indicators:
- Outbound connections from AcroRd32.exe to unknown external IPs
- DNS requests for suspicious domains following PDF opening
SIEM Query:
process_name:"AcroRd32.exe" AND (event_id:1000 OR parent_process_name:"AcroRd32.exe")