CVE-2025-29815: Microsoft Edge Use After Free Vulnerability

CVE-2025-29815 Overview

CVE-2025-29815 is a use-after-free vulnerability in Microsoft Edge (Chromium-based) that allows an authorized attacker to execute code over a network. The flaw is tracked under CWE-416 and affects the browser's memory management routines. Successful exploitation requires user interaction, such as visiting a malicious page or clicking a crafted link.

Microsoft published the advisory through the Microsoft Security Response Center (MSRC) and addressed the issue in updated Edge releases.

Critical Impact
An attacker who successfully exploits this vulnerability can execute arbitrary code in the context of the Edge browser process, leading to high confidentiality and integrity impact on the targeted system.

Affected Products

Microsoft Edge (Chromium-based) — versions prior to the April 2025 security update
Windows installations running vulnerable Edge builds
macOS installations running vulnerable Edge builds

Discovery Timeline

2025-04-04 - CVE-2025-29815 published to NVD
2025-07-09 - Last updated in NVD database

Technical Details for CVE-2025-29815

Vulnerability Analysis

The vulnerability is a use-after-free condition in Microsoft Edge (Chromium-based). The browser frees a memory object while another pointer continues to reference it. When that dangling pointer is later dereferenced, an attacker who controls the freed region's contents can hijack program flow.

The attack vector is network-based and requires both low-privilege authentication and user interaction. An attacker hosts a crafted web page or web content that triggers the vulnerable code path when rendered by Edge. The scope is unchanged, meaning code executes within the browser's security boundary.

Because Chromium-based browsers process untrusted HTML, JavaScript, and media on every page load, use-after-free defects in renderer components are common stepping stones in exploit chains. Attackers frequently combine memory corruption flaws with sandbox escapes to achieve full system compromise.

Root Cause

The root cause is improper object lifetime management in Edge's Chromium code base. A heap object is released while a stale reference remains live. Subsequent operations on the dangling reference produce undefined behavior that an attacker can shape into arbitrary code execution by performing heap grooming and replacing the freed allocation with attacker-controlled data.

Attack Vector

An authorized attacker delivers a malicious web resource to a victim using Edge. The victim must interact with the content, for example by browsing to the page or following a link. Rendering the content triggers the use-after-free, allowing the attacker to execute code with the privileges of the Edge process. Microsoft's advisory at MSRC CVE-2025-29815 provides additional context.

// No verified public proof-of-concept exists for CVE-2025-29815.
// Refer to the Microsoft advisory for technical details.

Detection Methods for CVE-2025-29815

Indicators of Compromise

Edge browser processes (msedge.exe) crashing or spawning unexpected child processes such as cmd.exe, powershell.exe, or rundll32.exe
Outbound network connections from Edge to unfamiliar domains immediately after a user visits an untrusted page
New persistence artifacts (scheduled tasks, registry Run keys, startup files) created within minutes of browser activity
Unexpected DLL loads or memory regions marked as executable inside the Edge process

Detection Strategies

Monitor parent-child process relationships originating from msedge.exe and alert on shell or scripting host children
Inspect EDR telemetry for in-memory code execution patterns, including suspicious VirtualAlloc and WriteProcessMemory activity within browser processes
Correlate browser crash events (Windows Event ID 1000) with subsequent process creation or network anomalies
Use behavioral analytics platforms such as Singularity Endpoint to identify post-exploitation actions following browser exploitation

Monitoring Recommendations

Centralize browser telemetry, EDR alerts, and proxy logs in a SIEM such as Singularity Data Lake for correlation across endpoints
Track Edge version inventory across the fleet to identify hosts still running vulnerable builds
Alert on first-seen domains accessed by Edge that immediately precede process anomalies
Review web proxy categorization logs for users accessing newly registered or low-reputation domains

How to Mitigate CVE-2025-29815

Immediate Actions Required

Update Microsoft Edge to the latest available version through the built-in updater or enterprise management tooling
Verify Edge auto-update is enabled across managed endpoints and not blocked by Group Policy
Restrict standard users from disabling browser updates and enforce update channels through edge://policy
Communicate phishing risk to end users, since exploitation requires user interaction with attacker-controlled content

Patch Information

Microsoft has released a security update through the Edge update channel. Review the Microsoft CVE-2025-29815 Advisory for the fixed build number and deployment guidance. Confirm patched versions in edge://settings/help after updates are applied.

Workarounds

Block access to untrusted or newly observed domains at the web proxy or DNS layer until patches are deployed
Enforce the Microsoft Edge SmartScreenEnabled and SmartScreenPuaEnabled policies to filter malicious sites
Limit browser execution to standard user contexts to constrain the impact of code execution
Apply application control policies that prevent msedge.exe from launching scripting hosts or unsigned binaries

bash

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

# Enforce Edge auto-update via Group Policy registry key
reg add "HKLM\SOFTWARE\Policies\Microsoft\EdgeUpdate" /v UpdateDefault /t REG_DWORD /d 1 /f