CVE-2025-8069: AWS Client VPN Privilege Escalation Flaw

CVE-2025-8069 Overview

CVE-2025-8069 is a local privilege escalation vulnerability affecting the AWS Client VPN client installation process on Windows devices. During installation, the process references a hardcoded directory path (C:\usr\local\windows-x86_64-openssl-localbuild\ssl) to fetch the OpenSSL configuration file. This insecure default configuration allows a non-privileged user to place arbitrary code in the configuration file location, which would then be executed with elevated privileges when an administrator initiates the AWS Client VPN installation process.

Critical Impact

A local attacker with standard user privileges can achieve root-level code execution by placing malicious configuration files in a predictable path, compromising the entire system when an administrator runs the VPN client installation.

Affected Products

• AWS Client VPN for Windows versions prior to 5.2.2

Discovery Timeline

• 2025-07-23 - CVE CVE-2025-8069 published to NVD
• 2025-10-14 - Last updated in NVD database

Technical Details for CVE-2025-8069

Vulnerability Analysis

This vulnerability stems from CWE-276: Incorrect Default Permissions, where the AWS Client VPN installation process on Windows references an unusual and potentially user-writable directory path for OpenSSL configuration. The hardcoded path C:\usr\local\windows-x86_64-openssl-localbuild\ssl appears to be a development artifact that should not exist in production software.

The exploitation scenario requires local access and hinges on the timing of when an administrator performs the VPN client installation. A non-admin user can pre-create the directory structure and place a malicious OpenSSL configuration file, which will then be processed with elevated privileges during installation.

This issue is specific to Windows devices and does not affect Linux or Mac deployments of the AWS Client VPN client.

Root Cause

The root cause is the use of an insecure, hardcoded directory path for OpenSSL configuration that exists outside of protected system directories. The path C:\usr\local\ is not a standard Windows protected location and can typically be created and modified by non-privileged users if it doesn't already exist. This violates the principle of least privilege, as the installation process should not reference user-writable locations when executing with elevated permissions.

Attack Vector

The attack vector is local, requiring the attacker to have prior access to the Windows system where AWS Client VPN will be installed. The attack sequence involves:

1. A non-privileged user creates the directory structure C:\usr\local\windows-x86_64-openssl-localbuild\ssl
2. The attacker places a malicious OpenSSL configuration file in this location
3. When an administrator runs the AWS Client VPN installer, the installation process reads and processes the attacker-controlled configuration
4. The malicious configuration triggers code execution with root-level privileges

The vulnerability requires the attacker to wait for or social engineer an administrator to perform the installation, introducing a timing element to the attack.

Detection Methods for CVE-2025-8069

Indicators of Compromise

• Unexpected directory creation at C:\usr\local\windows-x86_64-openssl-localbuild\ssl
• Presence of OpenSSL configuration files (e.g., openssl.cnf) in the above directory created by non-admin users
• File system modifications to the C:\usr\ directory tree by non-privileged accounts
• Unusual processes spawned during AWS Client VPN installation

Detection Strategies

• Monitor file system activity for creation of the C:\usr\local\ directory structure, which is atypical on Windows systems
• Implement file integrity monitoring (FIM) on system directories to detect unauthorized configuration files
• Use endpoint detection and response (EDR) solutions to track privilege escalation attempts during software installation processes
• Review Windows Security Event logs for file creation events in unusual paths by standard users

Monitoring Recommendations

• Configure SentinelOne to alert on directory creation matching the pattern C:\usr\local\* as this is an unusual path on Windows
• Enable process lineage tracking to identify child processes spawned from the AWS Client VPN installer with unexpected behaviors
• Implement behavioral analysis rules to detect local privilege escalation techniques during installation workflows
• Monitor for OpenSSL configuration file modifications that could indicate exploitation attempts

How to Mitigate CVE-2025-8069

Immediate Actions Required

• Discontinue any new installations of AWS Client VPN on Windows systems using versions prior to 5.2.2
• Upgrade existing AWS Client VPN installations to version 5.2.2 or later
• Check for the existence of the C:\usr\local\windows-x86_64-openssl-localbuild\ssl directory on systems where AWS Client VPN may be installed
• Remove any suspicious files found in the C:\usr\local\ directory tree
• Review installation logs for any AWS Client VPN installations performed while the vulnerable directory structure existed

Patch Information

AWS has addressed this vulnerability in AWS Client VPN version 5.2.2. Users should upgrade to this version or later to remediate the vulnerability. For detailed information, refer to the AWS Security Bulletin AWS-2025-014 and the AWS Client VPN Release Notes.

Workarounds

• Proactively create the C:\usr\local\windows-x86_64-openssl-localbuild\ssl directory with administrator-only permissions before any installation occurs
• Use Windows NTFS permissions to restrict access to the C:\usr\ directory tree if it exists
• Deploy the AWS Client VPN installer only from secure, administrator-controlled channels
• Consider using alternative VPN solutions until the patched version can be deployed

# PowerShell commands to prevent exploitation by creating protected directories
# Run as Administrator

# Create the directory structure with proper permissions
New-Item -Path "C:\usr\local\windows-x86_64-openssl-localbuild\ssl" -ItemType Directory -Force

# Set restrictive ACLs - only SYSTEM and Administrators can access
$acl = Get-Acl "C:\usr"
$acl.SetAccessRuleProtection($true, $false)
$adminRule = New-Object System.Security.AccessControl.FileSystemAccessRule("Administrators","FullControl","ContainerInherit,ObjectInherit","None","Allow")
$systemRule = New-Object System.Security.AccessControl.FileSystemAccessRule("SYSTEM","FullControl","ContainerInherit,ObjectInherit","None","Allow")
$acl.AddAccessRule($adminRule)
$acl.AddAccessRule($systemRule)
Set-Acl "C:\usr" $acl