CVE-2020-17058: Microsoft Edge Buffer Overflow Flaw

CVE-2020-17058 Overview

CVE-2020-17058 is a memory corruption vulnerability affecting Microsoft browsers, including Microsoft Edge and Internet Explorer 11. This vulnerability is classified as an Out-of-Bounds Write (CWE-787) flaw that could allow attackers to execute arbitrary code on affected systems. The vulnerability requires user interaction, typically through convincing a user to visit a specially crafted webpage or open a malicious document.

Critical Impact

Successful exploitation could enable an attacker to execute arbitrary code in the context of the current user, potentially leading to complete system compromise if the user has administrative privileges.

Affected Products

• Microsoft Edge (Legacy)
• Microsoft Internet Explorer 11
• Microsoft Windows 10 (multiple versions: 1607, 1803, 1809, 1903, 1909, 2004, 20H2)
• Microsoft Windows Server 2016
• Microsoft Windows Server 2019

Discovery Timeline

• 2020-11-11 - CVE-2020-17058 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-17058

Vulnerability Analysis

This memory corruption vulnerability exists in Microsoft's browser rendering engines. The flaw is categorized as CWE-787 (Out-of-Bounds Write), indicating that the affected browser components write data past the end or before the beginning of an intended buffer. When successfully exploited, this out-of-bounds write condition can corrupt adjacent memory, potentially allowing an attacker to overwrite critical data structures or inject malicious code into executable memory regions.

The vulnerability requires network-based delivery of malicious content and depends on user interaction. An attacker would need to convince a victim to visit a malicious website or open a crafted document that triggers the vulnerable code path in the browser's memory management routines.

Root Cause

The root cause of CVE-2020-17058 lies in improper bounds checking within the browser's memory handling operations. When processing certain types of web content, the browser fails to properly validate the size or boundaries of data being written to memory buffers. This allows specially crafted input to trigger writes beyond the allocated memory region, resulting in memory corruption that can be leveraged for code execution.

Attack Vector

The attack vector for this vulnerability is network-based, requiring an attacker to deliver malicious content to the victim's browser. Typical exploitation scenarios include:

1. Malicious Website: An attacker hosts a webpage containing exploit code that triggers the vulnerability when rendered by the victim's browser
2. Malvertising Campaigns: Embedding exploit code within advertising networks to reach victims through legitimate websites
3. Spear Phishing: Sending targeted emails with links to exploit pages or malicious attachments that open in the browser
4. Compromised Websites: Injecting exploit code into legitimate but compromised websites (watering hole attacks)

The vulnerability mechanism involves crafting specific HTML, JavaScript, or other web content that causes the browser to perform an out-of-bounds memory write during rendering or script execution. This memory corruption can then be chained with additional techniques to achieve reliable code execution within the context of the browser process.

Detection Methods for CVE-2020-17058

Indicators of Compromise

• Unexpected browser crashes or abnormal termination of iexplore.exe or MicrosoftEdge.exe processes
• Suspicious child processes spawned from browser processes, particularly command shells or PowerShell instances
• Network connections to unknown or malicious domains immediately following browser activity
• Memory access violations or exception logs in Windows Event logs related to browser processes

Detection Strategies

• Deploy endpoint detection rules monitoring for anomalous behavior from browser processes, including unusual memory allocation patterns
• Implement network-level inspection for known exploit kit signatures and malicious JavaScript patterns
• Configure browser crash monitoring and analysis to identify potential exploitation attempts
• Utilize SentinelOne's behavioral AI to detect post-exploitation activities such as process injection or suspicious child process creation

Monitoring Recommendations

• Enable enhanced logging for Internet Explorer and Edge browsers through Windows Event Logging
• Monitor for browser processes attempting to access sensitive system locations or spawn unexpected executables
• Implement real-time alerting for browser-related Application Crash events in Windows Event logs
• Track network traffic from browser processes for connections to newly registered or low-reputation domains

How to Mitigate CVE-2020-17058

Immediate Actions Required

• Apply the November 2020 Microsoft security updates immediately to all affected systems
• Consider migrating from Internet Explorer 11 and Legacy Edge to Microsoft Edge Chromium for improved security
• Implement network segmentation to limit the potential impact of successful exploitation
• Enable browser isolation features where available to contain potential exploits

Patch Information

Microsoft has released security updates to address this vulnerability as part of the November 2020 Patch Tuesday release cycle. Detailed patch information and download links are available in the Microsoft Security Advisory CVE-2020-17058.

Organizations should prioritize deployment of these patches, particularly on systems where users regularly browse the internet or access untrusted content. Server systems running Windows Server 2016 or 2019 with Internet Explorer enabled should also be patched, especially if they serve as Remote Desktop Session Hosts or Citrix servers.

Workarounds

• Restrict users from accessing untrusted websites using web filtering or proxy solutions until patches can be applied
• Disable active scripting in Internet Explorer through Internet Options security settings as a temporary measure
• Configure Enhanced Protected Mode in Internet Explorer to provide additional exploit mitigations
• Deploy SentinelOne Singularity Platform to detect and block exploitation attempts through behavioral analysis

# Disable Active Scripting in Internet Explorer via Registry (temporary mitigation)
reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3" /v "1400" /t REG_DWORD /d 3 /f
reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\4" /v "1400" /t REG_DWORD /d 3 /f