CVE-2021-28554
📋 TL;DR
This vulnerability in Adobe Acrobat Reader DC allows an attacker to read memory outside intended boundaries, potentially leading to arbitrary code execution when a user opens a malicious PDF file. It affects multiple versions of Acrobat Reader DC across different release tracks. Users who open untrusted PDF files are at risk.
💻 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 through arbitrary code execution with current user privileges, potentially leading to data theft, ransomware deployment, or lateral movement.
Likely Case
System compromise through malicious PDF files delivered via phishing or compromised websites, leading to credential theft or malware installation.
If Mitigated
Limited impact with proper security controls like application sandboxing, least privilege, and user awareness training preventing malicious file execution.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious PDF). No public exploit code known at time of advisory.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2021.001.20155 (for 2021 track), 2020.001.30025 (for 2020 track), 2017.011.30196 (for 2017 track) - update to versions after these
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 latest version. 4. Restart computer if required.
🔧 Temporary Workarounds
Disable JavaScript in Adobe Reader
allPrevents JavaScript-based exploitation vectors
Edit > Preferences > JavaScript > Uncheck 'Enable Acrobat JavaScript'
Use Protected View
allOpen untrusted PDFs in Protected View mode
File > Properties > Security > Enable Protected View for untrusted documents
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized PDF readers
- Deploy email/web gateways to block malicious PDF attachments and downloads
🔍 How to Verify
Check if Vulnerable:
Check Help > About Adobe Acrobat Reader DC and compare version to affected rangesCheck Version:
On Windows: wmic product where name="Adobe Acrobat Reader DC" get versionVerify Fix Applied:
Verify version is newer than affected versions: 2021.001.20156+, 2020.001.30026+, or 2017.011.30197+📡 Detection & Monitoring
Log Indicators:
- Adobe Reader crash logs with memory access violations
- Windows Event Logs showing AcroRd32.exe crashes
Network Indicators:
- PDF downloads from suspicious sources
- Unusual outbound connections after PDF opening
SIEM Query:
source="*acrobat*" AND (event_type="crash" OR error="out-of-bounds")