CVE-2021-21806
📋 TL;DR
This is a use-after-free vulnerability in WebKitGTK browser that allows remote code execution when users visit malicious websites. It affects WebKitGTK 2.30.3 x64 users, potentially compromising their systems through browser exploitation.
💻 Affected Systems
- WebKitGTK
📦 What is this software?
Webkitgtk by Webkitgtk
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining complete control over the victim's machine through remote code execution.
Likely Case
Browser compromise leading to data theft, malware installation, or lateral movement within the network.
If Mitigated
Limited impact if browser sandboxing works effectively, potentially only browser crash or denial of service.
🎯 Exploit Status
Exploitation requires user interaction (visiting malicious website) but no authentication; proof-of-concept details are publicly available in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: WebKitGTK 2.30.4 or later
Vendor Advisory: https://webkitgtk.org/security/WSA-2021-0005.html
Restart Required: Yes
Instructions:
1. Update WebKitGTK to version 2.30.4 or later using your distribution's package manager. 2. Restart all applications using WebKitGTK, including web browsers. 3. Verify the update was successful.
🔧 Temporary Workarounds
Disable JavaScript
linuxTemporarily disable JavaScript in WebKitGTK-based browsers to prevent exploitation
Browser-specific: In GNOME Web (Epiphany), go to Preferences > Privacy and disable JavaScript
Use alternative browser
linuxSwitch to non-WebKitGTK browsers until patched
🧯 If You Can't Patch
- Implement network filtering to block access to untrusted websites
- Use application whitelisting to prevent unauthorized code execution
🔍 How to Verify
Check if Vulnerable:
Check WebKitGTK version: `webkit2gtk-4.0 --version` or check package managerCheck Version:
webkit2gtk-4.0 --versionVerify Fix Applied:
Verify version is 2.30.4 or higher: `dpkg -l | grep webkit2gtk` or `rpm -qa | grep webkit2gtk`📡 Detection & Monitoring
Log Indicators:
- Browser crash logs with memory access violations
- Unexpected process creation from browser
Network Indicators:
- Connections to known malicious domains serving exploit code
SIEM Query:
process_name:webkit AND (event_id:1000 OR memory_violation) OR network_connection:malicious_domain