CVE-2024-21399: Microsoft Edge Chromium RCE Vulnerability

CVE-2024-21399 Overview

CVE-2024-21399 is a remote code execution vulnerability affecting Microsoft Edge (Chromium-based). Microsoft published the advisory on February 2, 2024. The flaw carries a CVSS 3.1 base score of 8.3 and is associated with [CWE-416] Use After Free. Successful exploitation enables an attacker to execute arbitrary code in the context of the browser and pivot beyond the browser sandbox, resulting in a scope change.

Exploitation requires user interaction, such as visiting an attacker-controlled web page. The vulnerability impacts confidentiality, integrity, and availability. No public proof-of-concept or in-the-wild exploitation has been documented at the time of writing.

Critical Impact
Remote attackers can achieve code execution on the host system through crafted web content, with the scope extending beyond the browser process boundary.

Affected Products

Microsoft Edge (Chromium-based) — all versions prior to the February 2024 security update
Windows-based Edge installations consuming the Chromium upstream
macOS and Linux Edge channels tracking the same Chromium release branch

Discovery Timeline

2024-02-02 - CVE-2024-21399 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-21399

Vulnerability Analysis

The vulnerability is classified under [CWE-416] Use After Free, a memory corruption class where a program continues to reference memory after it has been released. In Chromium-based browsers, use-after-free issues frequently appear in renderer components, IPC handlers, or extension subsystems where object lifetimes span multiple threads.

An attacker hosts crafted web content that triggers the freed-object reference path. When the victim loads the page, the browser dereferences a dangling pointer. The attacker can shape the freed allocation with controlled data to influence the execution path.

The CVSS vector indicates a scope change, meaning successful exploitation affects resources beyond the vulnerable component. In browser contexts, this typically maps to sandbox escape primitives that allow code execution outside the renderer process.

Root Cause

The root cause is improper object lifetime management within Microsoft Edge code paths that diverge from upstream Chromium. The vulnerable code releases an object while another reference path retains a pointer. Subsequent access to the freed object triggers undefined behavior that an attacker can shape into controlled execution.

Attack Vector

The attack vector is network-based. An attacker hosts a malicious page or compromises a trusted site to deliver the trigger payload. The victim must interact with the content — typically by visiting the page or activating an embedded element — for exploitation to succeed. High attack complexity reflects the precise heap grooming and timing required to win the use-after-free race.

No verified public exploit code is available. Technical details should be sourced from the Microsoft CVE-2024-21399 Advisory.

Detection Methods for CVE-2024-21399

Indicators of Compromise

Microsoft Edge renderer or broker process crashes correlated with specific page loads
Unexpected child processes spawned by msedge.exe outside normal browser workflows
Outbound connections from Edge processes to unrecognized infrastructure following web navigation
Edge installations reporting versions below the February 2024 security release

Detection Strategies

Inventory all Edge installations and flag any version preceding the February 2024 Microsoft security update
Monitor process creation events where msedge.exe spawns shells, scripting hosts, or LOLBins
Correlate browser crash telemetry (WerFault.exe invocations tied to msedge.exe) with browsing history for triage

Monitoring Recommendations

Enable browser telemetry forwarding to a central data lake for retrospective hunting against suspicious navigation patterns
Alert on Edge processes writing to autorun locations, scheduled tasks, or user startup folders
Track outbound network connections initiated by Edge child processes that bypass standard proxy egress points

How to Mitigate CVE-2024-21399

Immediate Actions Required

Update Microsoft Edge to the version listed in the Microsoft CVE-2024-21399 Advisory through edge://settings/help or managed deployment tooling
Verify enterprise update policies are not pinning Edge to a vulnerable build
Restrict browsing to trusted sites on systems that cannot be patched immediately

Patch Information

Microsoft released a fixed Edge build referenced in the Microsoft Security Response Center advisory for CVE-2024-21399. Administrators should validate the deployed version using msedge.exe --version and confirm it matches or exceeds the patched release. Group Policy or Microsoft Intune can enforce auto-update behavior across managed fleets.

Workarounds

Deploy site allow-lists via Edge enterprise policy to limit exposure to untrusted web content
Disable JIT compilation through the JavaScriptJitDisabledForSites policy where compatibility permits to reduce exploitability of memory corruption flaws
Enforce Microsoft Defender Application Guard or equivalent isolation for high-risk browsing sessions until patches are applied

bash

# Verify installed Edge version on Windows
"%ProgramFiles(x86)%\Microsoft\Edge\Application\msedge.exe" --version

# Force policy refresh after deploying enterprise update settings
gpupdate /force