CVE-2023-35618: Microsoft Edge Privilege Escalation Bug

CVE-2023-35618 Overview

CVE-2023-35618 is a critical elevation of privilege vulnerability affecting Microsoft Edge (Chromium-based). This vulnerability allows attackers to escalate privileges through network-based attacks, potentially gaining unauthorized access to sensitive system resources and data. The vulnerability is classified under CWE-416 (Use After Free), indicating a memory corruption flaw where the browser continues to reference memory after it has been freed.

Critical Impact

An attacker who successfully exploits this vulnerability could escape the browser sandbox and gain elevated privileges on the target system, potentially leading to complete system compromise with high impact on confidentiality, integrity, and availability.

Affected Products

• Microsoft Edge (Chromium-based) - all versions prior to the security patch
• Chromium-based browsers on Gentoo Linux (as referenced in GLSA 202402-05)
• Microsoft Edge Chromium across Windows platforms

Discovery Timeline

• 2023-12-07 - CVE-2023-35618 published to NVD
• 2025-01-01 - Last updated in NVD database

Technical Details for CVE-2023-35618

Vulnerability Analysis

This elevation of privilege vulnerability in Microsoft Edge stems from a Use After Free (UAF) memory corruption issue. In this type of vulnerability, the browser references a memory location that has already been deallocated, which can be exploited by attackers to execute arbitrary code or escalate privileges. The scope of impact extends beyond the vulnerable component itself, as successful exploitation allows the attacker to break out of the browser's security sandbox.

The vulnerability requires user interaction to exploit—typically through social engineering techniques that convince a user to visit a malicious webpage or click a crafted link. Once triggered, the attacker can leverage the memory corruption to gain elevated privileges on the affected system.

Root Cause

The vulnerability originates from improper memory management within the Chromium-based Edge browser. Specifically, a Use After Free condition (CWE-416) occurs when the browser fails to properly handle memory deallocation, allowing freed memory to be referenced and manipulated. This memory safety issue creates an exploitable condition where an attacker can control the contents of the freed memory region and redirect program execution.

Attack Vector

The attack is network-based, requiring an attacker to craft a malicious webpage or content that triggers the Use After Free condition. The exploitation flow typically involves:

1. The attacker hosts or injects malicious content on a web page
2. The victim visits the page using a vulnerable version of Microsoft Edge
3. The malicious content triggers the UAF condition in the browser
4. The attacker gains control over freed memory regions
5. Privilege escalation occurs, potentially allowing sandbox escape

The vulnerability does not require any special privileges to exploit, but it does require user interaction such as clicking a link or visiting a compromised website. Due to the changed scope indicator in the vulnerability assessment, successful exploitation can impact resources beyond the browser's security boundary.

Detection Methods for CVE-2023-35618

Indicators of Compromise

• Unusual browser crashes or unexpected Edge process behavior that may indicate memory corruption attempts
• Edge browser spawning child processes with elevated privileges
• Suspicious network connections originating from Microsoft Edge to unknown or untrusted domains
• Unexpected modifications to system files or registry entries following browser activity

Detection Strategies

• Monitor Microsoft Edge process behavior for anomalous memory access patterns or crashes
• Implement endpoint detection rules to identify Edge processes attempting privilege escalation
• Deploy network monitoring to detect connections to known malicious infrastructure
• Use browser telemetry to identify repeated crash patterns that may indicate exploitation attempts

Monitoring Recommendations

• Enable Windows Defender Application Guard for Edge to contain potential exploits
• Configure security information and event management (SIEM) rules to correlate Edge-related anomalies
• Monitor for unexpected Edge child processes with elevated token privileges
• Track browser version deployments to ensure all instances are patched

How to Mitigate CVE-2023-35618

Immediate Actions Required

• Update Microsoft Edge to the latest version immediately through Windows Update or the Microsoft Edge settings menu
• Verify all managed Edge installations across the enterprise are running patched versions
• Consider temporarily restricting access to untrusted websites until patches are deployed
• Enable browser isolation features such as Windows Defender Application Guard

Patch Information

Microsoft has released a security update to address CVE-2023-35618. Organizations should reference the Microsoft Security Update Guide for detailed patching information and affected version details. Gentoo Linux users should also consult the GLSA 202402-05 Advisory for platform-specific guidance.

To verify your Microsoft Edge version:

1. Open Microsoft Edge
2. Navigate to edge://settings/help
3. Confirm the browser version includes the security fix

Workarounds

• Enable Microsoft Defender Application Guard to isolate browser sessions from the host operating system
• Configure group policies to restrict Edge from executing content from untrusted sources
• Implement strict browser security policies using Microsoft Endpoint Manager
• Consider using a separate browser profile with restricted permissions for high-risk browsing activities

# Check Microsoft Edge version via PowerShell
Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Edge\BLBeacon' | Select-Object version

# Force Edge update via command line
start msedge --check-for-update-interval=1

# Enable Application Guard for Edge via PowerShell (Windows Enterprise)
Enable-WindowsOptionalFeature -Online -FeatureName Windows-Defender-ApplicationGuard