CVE-2021-34971
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on affected Foxit PDF Reader installations by tricking users into opening malicious PDF files containing specially crafted JPG2000 images. The flaw is a heap-based buffer overflow caused by improper length validation when parsing PDF files. Users of vulnerable Foxit PDF Reader versions are affected.
💻 Affected Systems
- Foxit PDF Reader
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control of the victim's machine, enabling data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Attacker executes malicious code with the same privileges as the PDF reader process, potentially leading to credential theft, malware installation, or data exfiltration.
If Mitigated
If proper controls are in place, the impact is limited to application crash or denial of service, with code execution prevented by security mitigations like ASLR or DEP.
🎯 Exploit Status
Exploitation requires user interaction but no authentication. The vulnerability was discovered by Zero Day Initiative (ZDI-CAN-14812), suggesting potential for weaponization.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.1.0.52543 and later
Vendor Advisory: https://www.foxit.com/support/security-bulletins.html
Restart Required: Yes
Instructions:
1. Open Foxit PDF Reader. 2. Go to Help > Check for Updates. 3. Follow prompts to download and install version 11.1.0.52543 or later. 4. Restart the application.
🔧 Temporary Workarounds
Disable JPG2000 parsing
windowsModify registry to disable JPG2000 image parsing in Foxit PDF Reader
reg add "HKCU\Software\Foxit Software\Foxit Reader\Preferences\Security" /v "bDisableJPX" /t REG_DWORD /d 1 /f
Use alternative PDF reader
allTemporarily use a different PDF reader application that is not vulnerable
🧯 If You Can't Patch
- Implement application whitelisting to prevent execution of unauthorized code
- Use network segmentation to limit lateral movement from compromised endpoints
🔍 How to Verify
Check if Vulnerable:
Open Foxit PDF Reader, go to Help > About, check if version is below 11.1.0.52543Check Version:
"C:\Program Files (x86)\Foxit Software\Foxit Reader\FoxitReader.exe" --versionVerify Fix Applied:
Verify Foxit PDF Reader version is 11.1.0.52543 or higher in Help > About📡 Detection & Monitoring
Log Indicators:
- Application crashes of FoxitReader.exe with exception codes like 0xC0000005 (ACCESS_VIOLATION)
- Unusual process creation from FoxitReader.exe
Network Indicators:
- Outbound connections from FoxitReader.exe to suspicious IPs/domains
- DNS requests for known malicious domains following PDF file access
SIEM Query:
process_name="FoxitReader.exe" AND (event_id=1000 OR event_id=1001) AND exception_code="0xC0000005"