CVE-2023-36735: Microsoft Edge Elevation Vulnerability

CVE-2023-36735 Overview

CVE-2023-36735 is an Elevation of Privilege vulnerability affecting Microsoft Edge (Chromium-based). This Use After Free (CWE-416) vulnerability allows attackers to gain elevated privileges through network-based attacks that require user interaction. The vulnerability affects the Chromium-based version of Microsoft's Edge browser and can lead to significant compromise of system confidentiality, integrity, and availability.

Critical Impact

This vulnerability enables attackers to escalate privileges through a Use After Free condition in Microsoft Edge Chromium, potentially allowing unauthorized access to sensitive system resources and the ability to execute code with elevated permissions.

Affected Products

• Microsoft Edge (Chromium-based)

Discovery Timeline

• September 15, 2023 - CVE-2023-36735 published to NVD
• January 1, 2025 - Last updated in NVD database

Technical Details for CVE-2023-36735

Vulnerability Analysis

This Elevation of Privilege vulnerability in Microsoft Edge (Chromium-based) stems from a Use After Free (UAF) memory corruption condition (CWE-416). UAF vulnerabilities occur when a program continues to reference memory after it has been freed, allowing an attacker to manipulate the freed memory location. In browser contexts, such vulnerabilities are particularly dangerous as they can be triggered through malicious web content.

The vulnerability requires user interaction, meaning a victim must be enticed to visit a malicious website or open a crafted document. However, the impact extends beyond the vulnerable component's security scope, potentially affecting other system resources and processes. Successful exploitation grants attackers the ability to compromise confidentiality, integrity, and availability of the target system.

Root Cause

The root cause of CVE-2023-36735 is a Use After Free condition within the Microsoft Edge Chromium browser. This occurs when memory that has been deallocated is subsequently accessed, creating an opportunity for attackers to corrupt memory structures or execute arbitrary code. The specific component containing this flaw has not been publicly detailed by Microsoft, but UAF vulnerabilities in browsers typically affect rendering engines, JavaScript engines, or component object models.

Attack Vector

The attack vector for this vulnerability is network-based, requiring user interaction to exploit. An attacker would need to craft malicious web content designed to trigger the Use After Free condition. When a victim navigates to the attacker-controlled content using a vulnerable version of Microsoft Edge, the exploitation sequence begins. The attack does not require authentication or prior access to the target system, making it accessible to remote attackers who can deliver malicious links through phishing campaigns, malicious advertisements, or compromised legitimate websites.

The vulnerability mechanism involves the browser processing web content that manipulates object lifetimes to create a dangling pointer condition. Once the freed memory is reallocated with attacker-controlled data, subsequent use of the dangling pointer can lead to privilege escalation. For detailed technical analysis, refer to the Microsoft Security Update Guide.

Detection Methods for CVE-2023-36735

Indicators of Compromise

• Unusual memory access patterns or crashes in Microsoft Edge processes (msedge.exe)
• Unexpected child process spawning from Edge browser processes
• Edge browser processes attempting to access or modify sensitive system resources
• Anomalous network connections originating from browser processes to unknown external hosts

Detection Strategies

• Monitor for Microsoft Edge process crashes that may indicate exploitation attempts
• Implement endpoint detection rules for suspicious process creation chains involving msedge.exe
• Deploy browser exploitation detection capabilities that identify memory corruption attempts
• Track Edge browser version inventory to identify unpatched installations across the environment

Monitoring Recommendations

• Enable enhanced logging for Microsoft Edge processes on endpoints
• Configure SIEM rules to correlate Edge-related events with potential exploitation indicators
• Implement network monitoring for suspicious outbound connections from browser processes
• Monitor for privilege escalation attempts following browser process activity

How to Mitigate CVE-2023-36735

Immediate Actions Required

• Update Microsoft Edge to the latest available version immediately
• Review Microsoft's security advisory for specific version remediation guidance
• Enable automatic updates for Microsoft Edge across all managed systems
• Consider implementing browser isolation technologies for high-risk users

Patch Information

Microsoft has released security updates to address this vulnerability. Organizations should consult the Microsoft Security Update Guide for CVE-2023-36735 for specific patch details and affected version information. Gentoo Linux users should also review GLSA 202402-05 for distribution-specific guidance.

Workarounds

• Implement web content filtering to block access to known malicious domains
• Deploy application allowlisting to restrict execution of unauthorized code
• Use network segmentation to limit the impact of potential browser compromises
• Consider using alternative browsers temporarily until patches can be applied to high-risk systems

# Verify Microsoft Edge version via command line
# Windows PowerShell
(Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Edge\BLBeacon').version

# Force Edge update check
"C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe" --check-for-update-interval=1