CVE-2025-21342: Microsoft Edge Chromium RCE Vulnerability

CVE-2025-21342 Overview

CVE-2025-21342 is a Remote Code Execution vulnerability affecting Microsoft Edge (Chromium-based). This type confusion vulnerability (CWE-843) allows attackers to execute arbitrary code on affected systems through specially crafted web content. The vulnerability can be exploited remotely over the network when a user visits a malicious website or interacts with attacker-controlled content in the browser.

Critical Impact

Successful exploitation enables remote attackers to execute arbitrary code with the privileges of the current user, potentially leading to complete system compromise, data theft, and lateral movement within enterprise environments.

Affected Products

• Microsoft Edge (Chromium-based)

Discovery Timeline

• 2025-02-06 - CVE-2025-21342 published to NVD
• 2025-02-11 - Last updated in NVD database

Technical Details for CVE-2025-21342

Vulnerability Analysis

This vulnerability is classified as a Type Confusion issue (CWE-843), which occurs when a program allocates or initializes a resource using one type but later accesses that resource using a type that is incompatible with the original type. In the context of Microsoft Edge's Chromium-based engine, type confusion vulnerabilities typically arise in the JavaScript engine (V8) or rendering components where objects are misinterpreted as different types than they actually are.

The attack requires user interaction - specifically, a victim must navigate to attacker-controlled content or a compromised legitimate website. Once triggered, the vulnerability allows for complete compromise of confidentiality, integrity, and availability on the affected system.

Root Cause

The root cause is a Type Confusion vulnerability (CWE-843) within Microsoft Edge's Chromium-based architecture. Type confusion occurs when code does not verify the type of an object passed to it before processing, leading to operations being performed on memory structures that do not match the expected type. This can result in accessing memory outside of allocated boundaries or interpreting data in unintended ways, ultimately enabling code execution.

Attack Vector

The attack is network-based and requires user interaction. An attacker would need to convince a user to visit a specially crafted webpage or click a malicious link. The exploitation does not require any privileges on the target system, making it particularly dangerous for drive-by download scenarios. Once a user accesses the malicious content through Microsoft Edge, the type confusion flaw can be triggered to achieve arbitrary code execution.

The vulnerability's network attack vector combined with low attack complexity means that exploitation scenarios could include:

• Malicious advertisements served through legitimate ad networks
• Compromised websites with injected exploit code
• Phishing campaigns directing users to attacker-controlled pages
• Malicious links shared via email or messaging platforms

Detection Methods for CVE-2025-21342

Indicators of Compromise

• Unexpected Microsoft Edge crashes followed by suspicious process spawning
• Anomalous network connections originating from msedge.exe to unknown external hosts
• Creation of suspicious child processes by Microsoft Edge outside normal browsing behavior
• Unusual memory allocation patterns or heap spray indicators in Edge processes

Detection Strategies

• Monitor for msedge.exe spawning unexpected child processes such as cmd.exe, powershell.exe, or wscript.exe
• Implement behavioral detection rules for type confusion exploitation patterns in browser processes
• Deploy endpoint detection and response (EDR) solutions capable of detecting in-memory exploitation techniques
• Enable Windows Defender Exploit Guard with Attack Surface Reduction (ASR) rules for browser protection

Monitoring Recommendations

• Configure security information and event management (SIEM) to alert on anomalous Edge browser behavior
• Enable enhanced logging for browser process activity and network connections
• Monitor for attempts to disable browser security features or sandbox escape indicators
• Track JavaScript execution anomalies that may indicate exploit delivery attempts

How to Mitigate CVE-2025-21342

Immediate Actions Required

• Update Microsoft Edge to the latest version immediately through Settings > About Microsoft Edge or via enterprise patch management
• Enable automatic updates for Microsoft Edge to ensure timely protection against future vulnerabilities
• Review and restrict browsing permissions for high-risk users until patching is complete
• Consider temporarily using alternative browsers for critical business operations if immediate patching is not possible

Patch Information

Microsoft has released a security update to address this vulnerability. Organizations should consult the Microsoft Security Response Center advisory for specific patch details and download links. The update should be applied through standard Microsoft update channels, including Windows Update, Microsoft Update Catalog, or enterprise deployment tools such as WSUS and SCCM.

Workarounds

• Enable Microsoft Defender SmartScreen to provide additional protection against malicious websites
• Implement network-level filtering to block access to known malicious domains
• Configure Content Security Policy headers on internal web applications to reduce exploitation surface
• Apply the principle of least privilege to limit the impact of successful exploitation
• Consider enabling Enhanced Security Mode in Microsoft Edge which provides additional mitigations

# Verify Microsoft Edge version via command line
# Run in PowerShell to check current Edge version
(Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\msedge.exe")."(Default)" | ForEach-Object { (Get-Item $_).VersionInfo.ProductVersion }

# Force Edge update check via registry (Enterprise environments)
# Ensure automatic updates are enabled
reg query "HKLM\SOFTWARE\Policies\Microsoft\EdgeUpdate" /v UpdateDefault