CVE-2021-34976
📋 TL;DR
CVE-2021-34976 is a use-after-free vulnerability in Foxit PDF Reader's PDF file parsing that allows remote attackers to disclose sensitive information. Users who open malicious PDF files or visit malicious web pages are affected. This vulnerability can be combined with other exploits to potentially execute arbitrary code.
💻 Affected Systems
- Foxit PDF Reader
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers combine this information disclosure with other vulnerabilities to achieve remote code execution, potentially gaining full control of the system.
Likely Case
Sensitive information disclosure from memory, potentially exposing credentials, session data, or other confidential information.
If Mitigated
Information disclosure limited to non-critical data with proper sandboxing and memory protections in place.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious file) and typically needs to be combined with other vulnerabilities for code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Foxit PDF Reader 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 update to version 11.1.0.52543 or later. 4. Restart the application.
🔧 Temporary Workarounds
Disable JavaScript in PDF Reader
allPrevents exploitation through malicious JavaScript in PDF files
In Foxit Reader: File > Preferences > JavaScript > Uncheck 'Enable JavaScript'
Use Protected View
allOpen PDFs in protected/sandboxed mode to limit potential damage
In Foxit Reader: File > Preferences > Trust Manager > Enable 'Safe Reading Mode'
🧯 If You Can't Patch
- Restrict PDF file opening to trusted sources only
- Use alternative PDF readers that are not affected by this vulnerability
🔍 How to Verify
Check if Vulnerable:
Check Foxit PDF Reader version: Help > About Foxit Reader. If version is below 11.1.0.52543, you are vulnerable.Check Version:
On Windows: wmic product where "name like 'Foxit%'" get versionVerify Fix Applied:
Verify version is 11.1.0.52543 or higher in Help > About Foxit Reader.📡 Detection & Monitoring
Log Indicators:
- Application crashes in Foxit Reader
- Unexpected memory access errors in application logs
Network Indicators:
- Downloads of PDF files from suspicious sources
- Network traffic to known malicious domains after PDF opening
SIEM Query:
source="*foxit*" AND (event_type="crash" OR error="access_violation")