CVE-2021-28560
📋 TL;DR
This heap-based buffer overflow vulnerability in Adobe Acrobat Reader DC allows an unauthenticated attacker to execute arbitrary code on a victim's system by tricking them into opening a malicious PDF file. It affects multiple versions across the 2021, 2020, and 2017 release streams. Successful exploitation gives the attacker the same privileges as the current user.
💻 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 full control of the victim's computer, enabling data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Malware installation leading to data exfiltration, credential theft, or system disruption through ransomware or other malicious payloads.
If Mitigated
Limited impact with proper security controls preventing successful exploitation or containing the damage through application sandboxing and privilege restrictions.
🎯 Exploit Status
Exploitation requires user interaction (opening a malicious PDF) but no authentication. The heap-based nature makes exploitation somewhat complex but feasible for skilled attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2021.001.20155, 2020.001.30025, 2017.011.30199 or later
Vendor Advisory: https://helpx.adobe.com/security/products/acrobat/apsb21-29.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 be used in conjunction with this vulnerability
Edit > Preferences > JavaScript > Uncheck 'Enable Acrobat JavaScript'
Use Protected View
allOpen untrusted PDFs in Protected View mode to limit potential damage
File > Properties > Security > Enable Protected View for untrusted documents
🧯 If You Can't Patch
- Restrict PDF file handling to alternative PDF readers that are not vulnerable
- Implement application whitelisting to block unauthorized code execution
🔍 How to Verify
Check if Vulnerable:
Check Adobe Reader version via Help > About Adobe Acrobat Reader DC and compare against affected versionsCheck Version:
On Windows: wmic product where name="Adobe Acrobat Reader DC" get versionVerify Fix Applied:
Verify version is 2021.001.20155+, 2020.001.30025+, or 2017.011.30199+📡 Detection & Monitoring
Log Indicators:
- Adobe Reader crash logs with heap corruption indicators
- Windows Event Logs showing unexpected process termination
Network Indicators:
- Unusual outbound connections from Adobe Reader process
- PDF downloads from suspicious sources
SIEM Query:
process_name:"AcroRd32.exe" AND (event_id:1000 OR event_id:1001) AND exception_code:0xc0000005