CVE-2021-31982
📋 TL;DR
This vulnerability allows attackers to bypass security features in Microsoft Edge (Chromium-based), potentially enabling malicious websites to execute unauthorized actions. It affects all users running vulnerable versions of Microsoft Edge on Windows, macOS, and Linux systems. The bypass could lead to privilege escalation or other security boundary violations.
💻 Affected Systems
- Microsoft Edge (Chromium-based)
📦 What is this software?
Edge Chromium by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through privilege escalation, allowing attackers to execute arbitrary code with elevated privileges, access sensitive data, or install persistent malware.
Likely Case
Malicious websites bypassing security controls to perform unauthorized actions like accessing local resources, stealing session data, or conducting phishing attacks with elevated permissions.
If Mitigated
Limited impact with proper security controls; attackers may bypass some security features but would be contained by other defense layers like application sandboxing and network segmentation.
🎯 Exploit Status
As a security feature bypass vulnerability, exploitation typically requires user interaction (visiting malicious website) but no authentication. Complexity is low once the bypass method is known.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 91.0.864.41 and later
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-31982
Restart Required: Yes
Instructions:
1. Open Microsoft Edge. 2. Click the three-dot menu → Help and feedback → About Microsoft Edge. 3. Browser will automatically check for updates and install if available. 4. Restart Edge when prompted. Alternatively, use enterprise deployment tools like Microsoft Intune or SCCM for organizational deployment.
🔧 Temporary Workarounds
Disable JavaScript (temporary)
allTemporarily disable JavaScript to prevent exploitation while patching, though this breaks most website functionality.
edge://settings/content/javascript
Use Application Guard
windowsEnable Microsoft Defender Application Guard for Edge to isolate browser sessions in a container.
Enable via Windows Features or Group Policy
🧯 If You Can't Patch
- Implement network filtering to block known malicious websites and restrict browser access to untrusted sites
- Use application control policies to restrict Edge's capabilities and enforce security baselines
🔍 How to Verify
Check if Vulnerable:
Open Edge, go to edge://settings/help. If version is below 91.0.864.41, system is vulnerable.Check Version:
edge://settings/help or check 'About Microsoft Edge' in browser menuVerify Fix Applied:
After update, verify version is 91.0.864.41 or higher in edge://settings/help.📡 Detection & Monitoring
Log Indicators:
- Unusual Edge process behavior, unexpected privilege escalation events, security feature bypass alerts in Windows Event Logs
Network Indicators:
- Connections to known malicious domains from Edge processes, unusual outbound traffic patterns
SIEM Query:
source="Microsoft-Windows-Security-Auditing" EventID=4688 | where ProcessName contains "msedge.exe" | where CommandLine contains suspicious patterns