CVE-2025-59251: Microsoft Edge Chromium RCE Vulnerability

CVE-2025-59251 Overview

CVE-2025-59251 is a remote code execution vulnerability in Microsoft Edge (Chromium-based). The flaw combines a stack-based buffer overflow [CWE-121] with improper control of code generation [CWE-94]. An attacker who convinces an authenticated user to interact with malicious web content can execute code in the browser process context. Microsoft published the advisory through the Microsoft Security Response Center (MSRC).

The vulnerability requires user interaction and low-level privileges, but the network attack vector makes drive-by exploitation and phishing-driven delivery practical.

Critical Impact

Successful exploitation allows code execution within Microsoft Edge with high confidentiality and integrity impact, exposing browser session data, credentials, and stored content.

Affected Products

• Microsoft Edge (Chromium-based) - versions prior to the September 2025 security update
• Windows installations running vulnerable Edge builds
• macOS and Linux installations running vulnerable Edge builds

Discovery Timeline

• 2025-09-24 - CVE-2025-59251 published to NVD
• 2025-11-20 - Last updated in NVD database

Technical Details for CVE-2025-59251

Vulnerability Analysis

The vulnerability stems from two related weakness classes identified in the CVE metadata: a stack-based buffer overflow [CWE-121] and improper control of code generation [CWE-94]. The combination indicates that crafted input handled by Edge can corrupt stack memory and influence dynamically generated code paths within the renderer or browser process.

An attacker hosts malicious content on a controlled web resource and lures an authenticated Edge user to load it. When the browser parses the attacker-controlled input, the stack overflow corrupts return addresses or function pointers. The code generation flaw allows the attacker to redirect execution into attacker-influenced instructions.

The attack delivers high impact to confidentiality and integrity, with limited availability impact. The scope remains unchanged, meaning code executes within the browser's sandboxed process boundary unless chained with a sandbox escape.

Root Cause

The root cause involves insufficient bounds checking on stack-allocated buffers combined with improper neutralization of input used to generate code [CWE-94]. The browser writes attacker-controlled data past the intended stack buffer boundary, corrupting adjacent control structures. Refer to the Microsoft Security Update Guide for vendor-confirmed technical details.

Attack Vector

Exploitation requires network delivery and user interaction. A user with a valid Edge session must navigate to a malicious page or open crafted content. Common delivery methods include phishing links, malvertising, and compromised legitimate sites that serve the exploit payload to visitors using vulnerable Edge versions.

Detection Methods for CVE-2025-59251

Indicators of Compromise

• Unexpected child processes spawned by msedge.exe, particularly command interpreters such as cmd.exe, powershell.exe, or wscript.exe
• Edge renderer or browser process crashes correlated with visits to untrusted domains
• Outbound connections from Edge processes to unfamiliar IP addresses or low-reputation domains shortly after page navigation

Detection Strategies

• Monitor process lineage for msedge.exe parent-child relationships that deviate from baseline behavior
• Inspect Windows Event Logs and crash dumps for Edge process termination signatures consistent with memory corruption
• Correlate web proxy logs with endpoint telemetry to identify users visiting domains serving exploit content

Monitoring Recommendations

• Enable browser telemetry forwarding to centralized logging for retrospective analysis
• Track Edge version inventory across managed endpoints to confirm patch coverage
• Alert on unsigned binary execution following Edge sessions to catch post-exploitation payload drops

How to Mitigate CVE-2025-59251

Immediate Actions Required

• Update Microsoft Edge to the latest stable channel build that addresses CVE-2025-59251
• Verify automatic update mechanisms are enabled and not blocked by group policy
• Restrict access to untrusted websites through enterprise web filtering until patches deploy

Patch Information

Microsoft released a security update for Edge addressing this vulnerability. Administrators should consult the Microsoft Security Update Guide for CVE-2025-59251 for the specific fixed version and deployment guidance. Edge typically updates automatically, but managed environments should validate update delivery.

Workarounds

• Deploy enterprise SmartScreen and web filtering to block known malicious domains
• Apply the principle of least privilege so Edge runs without administrative rights
• Use application control policies to limit child process execution from browser processes

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

# Force Edge update check via command line
"%ProgramFiles(x86)%\Microsoft\EdgeUpdate\MicrosoftEdgeUpdate.exe" /ua /installsource scheduler