CVE-2024-21385: Microsoft Edge Privilege Escalation Flaw

CVE-2024-21385 Overview

CVE-2024-21385 is an elevation of privilege vulnerability in Microsoft Edge (Chromium-based). The flaw is associated with a use-after-free condition [CWE-416] in the browser. An attacker who successfully exploits this vulnerability can elevate privileges within the context of the affected browser process.

Exploitation requires user interaction over a network attack vector. The vulnerability carries a CVSS 3.1 base score of 8.3 with a scope change, meaning successful exploitation can impact resources beyond the vulnerable component. Microsoft published the advisory through the Microsoft Security Response Center (MSRC) update guide.

Critical Impact
Successful exploitation allows an attacker to elevate privileges and compromise confidentiality, integrity, and availability of the affected system through the browser process.

Affected Products

Microsoft Edge (Chromium-based) - all versions prior to the security update addressing CVE-2024-21385
Windows systems running vulnerable Edge Chromium installations
Environments where Microsoft Edge is used as the primary or default browser

Discovery Timeline

2024-01-26 - CVE-2024-21385 published to the National Vulnerability Database (NVD)
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-21385

Vulnerability Analysis

The vulnerability is categorized as a use-after-free condition [CWE-416] in Microsoft Edge (Chromium-based). Use-after-free flaws occur when a program references memory after it has been released. Attackers can leverage this dangling reference to manipulate freed memory regions and influence program execution flow.

In the context of Edge Chromium, exploitation results in elevation of privilege rather than direct remote code execution. The scope change indicated in the CVSS vector signals that the compromised browser process can affect resources beyond its original security boundary. This typically means the attacker can escape sandbox restrictions or gain access to higher-privileged components.

The attack complexity is rated high, indicating that exploitation depends on conditions outside the attacker's control. Successful exploitation still produces high confidentiality, integrity, and availability impacts on the target system.

Root Cause

The root cause is improper memory management within Microsoft Edge Chromium. A code path frees a memory object while another reference to that memory remains active. When the dangling reference is later dereferenced, the attacker can control the contents of the previously freed allocation and redirect execution or escalate privileges.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker hosts a malicious web page or delivers crafted web content to a victim. The victim must visit the attacker-controlled page or interact with crafted content in Edge for exploitation to succeed. No prior authentication is required.

Verified exploitation code is not publicly available. Refer to the Microsoft CVE-2024-21385 Update for vendor technical details.

Detection Methods for CVE-2024-21385

Indicators of Compromise

Unexpected Microsoft Edge child process crashes or WerFault.exe events tied to msedge.exe
Edge processes spawning unusual child processes such as cmd.exe, powershell.exe, or script interpreters
Outbound network connections from Edge to unfamiliar domains immediately preceding privilege-related events
Anomalous file writes or registry modifications originating from the Edge process tree

Detection Strategies

Monitor browser process integrity levels and alert on transitions from low or medium to high integrity
Implement EDR rules that flag suspicious child process creation from msedge.exe
Correlate browser navigation telemetry with subsequent process and file system activity
Track Edge version compliance across the fleet to identify unpatched endpoints

Monitoring Recommendations

Enable verbose process creation logging (Windows Event ID 4688) with command-line auditing on endpoints running Edge
Forward browser telemetry and endpoint events to a centralized analytics platform for correlation
Establish baselines for normal Edge process behavior to surface deviations quickly
Review web proxy and DNS logs for connections to known malicious infrastructure following Edge launches

How to Mitigate CVE-2024-21385

Immediate Actions Required

Apply the security update referenced in the Microsoft CVE-2024-21385 advisory as soon as possible
Verify Microsoft Edge is configured to receive automatic updates across all managed endpoints
Audit endpoint inventories to confirm no legacy Edge Chromium versions remain in production
Restrict browsing to trusted sites on systems that cannot be patched immediately

Patch Information

Microsoft has released a security update for Microsoft Edge (Chromium-based) addressing CVE-2024-21385. Administrators should consult the Microsoft Security Response Center advisory for the specific patched build numbers and deployment guidance. Edge typically updates automatically, but enterprise environments using managed update channels should confirm the patched version is deployed.

Workarounds

Enforce strict web filtering policies to block access to untrusted or uncategorized sites
Disable or restrict execution of Edge extensions from untrusted sources until patching is complete
Use application control policies to prevent Edge child processes from launching script interpreters or shells
Educate users about avoiding unsolicited links and untrusted attachments that route through the browser

bash

# Verify the installed Microsoft Edge version on Windows endpoints
reg query "HKLM\SOFTWARE\Microsoft\Edge\BLBeacon" /v version

# Force Edge update check via the management policy registry key
reg add "HKLM\SOFTWARE\Policies\Microsoft\EdgeUpdate" /v UpdateDefault /t REG_DWORD /d 1 /f