AWS Client VPN for Windows Flaw Allows Attackers to Escalate Privileges

Amazon Web Services has disclosed a serious security vulnerability affecting its Client VPN software for Windows that could allow attackers to gain administrator-level access to affected systems.

The flaw, designated CVE-2025-8069, represents a significant risk for organizations using AWS’s managed VPN solution.

The vulnerability stems from a flawed installation process in the AWS Client VPN Windows client software.

During installation, the software references a specific directory path at C:\usr\local\windows-x86_64-openssl-localbuild\ssl to retrieve OpenSSL configuration files.

This behavior creates a dangerous security gap that malicious actors can exploit.

How the Attack Works

The exploitation method is particularly concerning because it leverages the trust relationship between different user privilege levels.

A non-administrative user can place malicious code within the OpenSSL configuration file in the referenced directory.

When an administrator subsequently runs the AWS Client VPN installation process, this malicious code executes with full administrative privileges, effectively allowing the attacker to take complete control of the system.

This type of vulnerability, known as a local privilege escalation flaw, is especially dangerous in corporate environments where standard users might have physical access to machines but lack administrative rights.

The attack vector could potentially be used to install persistent malware, steal sensitive data, or establish backdoors for future access.

Scope and Impact

The vulnerability affects multiple versions of the AWS Client VPN client, including versions 4.1.0, 5.0.0, 5.0.1, 5.0.2, 5.1.0, 5.2.0, and 5.2.1. Importantly, the flaw only impacts Windows installations—Linux and macOS versions of the client remain unaffected.

AWS Client VPN is a widely used managed service that provides secure access to both AWS cloud resources and on-premises networks.

Organizations across various industries rely on this service for remote workforce connectivity, making the vulnerability’s potential impact significant.

Resolution and Recommendations

Amazon has released AWS Client VPN Client version 5.2.2 to address this security issue.

The company strongly recommends that users immediately discontinue any new installations of versions prior to 5.2.2 on Windows systems.

The vulnerability was discovered through collaboration with the Zero Day Initiative, a well-known security research organization that operates a coordinated disclosure program for reporting vulnerabilities to vendors.

Security Implications

This incident highlights the ongoing challenges software vendors face in securing installation processes, particularly when dealing with file system permissions and directory structures.

Organizations should prioritize updating to the patched version and review their VPN client deployment procedures to ensure security best practices are followed.

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