CVE-2020-26534
📋 TL;DR
This CVE describes a use-after-free vulnerability in Foxit Reader and PhantomPDF's AcroForm JavaScript engine. Attackers can exploit this by crafting malicious PDF files to execute arbitrary code on vulnerable systems. All users running affected versions of Foxit Reader or PhantomPDF are at risk.
💻 Affected Systems
- Foxit Reader
- Foxit PhantomPDF
📦 What is this software?
Foxit Reader by Foxitsoftware
Phantompdf by Foxitsoftware
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with SYSTEM/administrator privileges leading to complete system compromise, data theft, ransomware deployment, or lateral movement within networks.
Likely Case
Arbitrary code execution with user-level privileges when a victim opens a malicious PDF document, potentially leading to malware installation, credential theft, or data exfiltration.
If Mitigated
Limited impact with proper application sandboxing, memory protection mechanisms, and user awareness preventing malicious PDF execution.
🎯 Exploit Status
Exploitation requires user interaction to open malicious PDF but requires minimal technical skill once PoC is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.1 and later
Vendor Advisory: https://www.foxitsoftware.com/support/security-bulletins.html
Restart Required: No
Instructions:
1. Download Foxit Reader/PhantomPDF 10.1 or later from official website. 2. Run installer. 3. Follow installation prompts. 4. Verify version in Help > About.
🔧 Temporary Workarounds
Disable JavaScript in Foxit
allPrevents AcroForm JavaScript execution that triggers the vulnerability
Open Foxit > File > Preferences > JavaScript > Uncheck 'Enable JavaScript'
Use Alternative PDF Viewer
allTemporarily switch to non-vulnerable PDF software
🧯 If You Can't Patch
- Implement application whitelisting to block Foxit Reader/PhantomPDF execution
- Deploy memory protection controls like DEP and ASLR system-wide
🔍 How to Verify
Check if Vulnerable:
Check Foxit version in Help > About. If version is below 10.1, system is vulnerable.Check Version:
On Windows: wmic product where name="Foxit Reader" get versionVerify Fix Applied:
Confirm version is 10.1 or higher in Help > About and verify JavaScript remains disabled if using workaround.📡 Detection & Monitoring
Log Indicators:
- Foxit crash logs with memory access violations
- Windows Event Logs showing Foxit process termination
Network Indicators:
- Unusual outbound connections from Foxit process
- PDF downloads from suspicious sources
SIEM Query:
process_name="FoxitReader.exe" AND (event_id=1000 OR event_id=1001) AND exception_code=c0000005