CVE-2021-42319: Visual Studio 2017 Privilege Escalation

CVE-2021-42319 Overview

CVE-2021-42319 is an Elevation of Privilege vulnerability affecting Microsoft Visual Studio 2017 and Visual Studio 2019. This vulnerability allows a locally authenticated attacker to exploit improper privilege management within Visual Studio components to gain elevated privileges on the affected system. The vulnerability stems from improper privilege management (CWE-269) in the Visual Studio development environment.

Critical Impact

A local attacker with low privileges can exploit this vulnerability to cause a denial of service condition, impacting the availability of Visual Studio development environments.

Affected Products

• Microsoft Visual Studio 2017
• Microsoft Visual Studio 2019

Discovery Timeline

• 2021-11-10 - CVE-2021-42319 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-42319

Vulnerability Analysis

This elevation of privilege vulnerability exists in Microsoft Visual Studio due to improper privilege management. The flaw is classified under CWE-269 (Improper Privilege Management), which occurs when software does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

The vulnerability requires local access to the affected system, meaning an attacker must already have some level of access to the target machine. While the attack complexity is low and no user interaction is required, the attacker does need low-level privileges to initiate the exploit. The primary impact of successful exploitation is availability degradation, resulting in denial of service conditions within the Visual Studio environment.

Root Cause

The root cause of CVE-2021-42319 is improper privilege management within Visual Studio's internal components. This weakness occurs when the application fails to properly restrict privileges during certain operations, allowing a user with limited privileges to affect system availability. The flaw is specifically tied to how Visual Studio handles privilege transitions and access control checks for local operations.

Attack Vector

The attack vector is local, requiring the attacker to have physical or remote authenticated access to the target system. The attacker must execute malicious code or perform specific operations within the Visual Studio environment to trigger the vulnerability. Due to the local nature of this attack, exploitation typically occurs on developer workstations where Visual Studio is installed.

An attacker with low-level user access could craft specific inputs or sequences of operations that exploit the improper privilege management flaw, leading to elevated operations that affect system availability. The exploitation does not result in confidentiality or integrity impacts, but primarily causes denial of service conditions.

Detection Methods for CVE-2021-42319

Indicators of Compromise

• Unexpected crashes or hangs in Visual Studio processes (devenv.exe)
• Unusual resource consumption by Visual Studio-related processes
• Error logs indicating privilege-related failures in Visual Studio event logs
• Abnormal termination of Visual Studio services or components

Detection Strategies

• Monitor for unusual process behavior associated with devenv.exe and related Visual Studio processes
• Implement endpoint detection rules for privilege escalation attempts on development workstations
• Enable Windows Security Event logging for privilege use (Event IDs 4672, 4673, 4674)
• Deploy behavioral analysis to detect anomalous Visual Studio process activity

Monitoring Recommendations

• Configure centralized logging for all Visual Studio installations across the enterprise
• Implement alerts for repeated Visual Studio crashes or availability issues
• Monitor system resource utilization on developer workstations for abnormal patterns
• Review Visual Studio diagnostic logs for privilege-related error messages

How to Mitigate CVE-2021-42319

Immediate Actions Required

• Apply the latest security updates from Microsoft for Visual Studio 2017 and Visual Studio 2019
• Review and restrict local access to development workstations
• Ensure endpoint protection solutions are updated with the latest detection capabilities
• Audit user accounts with access to Visual Studio installations and apply least privilege principles

Patch Information

Microsoft has released security updates to address CVE-2021-42319. System administrators should consult the Microsoft Security Advisory CVE-2021-42319 for detailed patch information and update guidance. Updates should be applied through Windows Update, Microsoft Update Catalog, or Visual Studio's built-in update mechanism.

Ensure Visual Studio installations are updated to the latest available versions that include the security fix for this vulnerability.

Workarounds

• Restrict local access to systems running Visual Studio to only authorized developers
• Implement application whitelisting to prevent unauthorized code execution
• Enable User Account Control (UAC) at the highest security level on developer workstations
• Consider running Visual Studio in a sandboxed or virtualized environment for high-security scenarios

# Configuration example - Enable enhanced auditing for privilege use
# Run in elevated PowerShell to enable auditing policies

# Enable audit policy for Privilege Use
auditpol /set /subcategory:"Sensitive Privilege Use" /success:enable /failure:enable

# Enable audit policy for Special Logon
auditpol /set /subcategory:"Special Logon" /success:enable /failure:enable

# Verify Visual Studio update status via command line
"C:\Program Files\Microsoft Visual Studio\Installer\vs_installer.exe" update --installPath "C:\Program Files\Microsoft Visual Studio\2019\Professional"