A critical security vulnerability, identified as CVE-2024-8474, has been discovered in OpenVPN Connect, the popular open-source Virtual Private Network (VPN) software. This vulnerability affects versions of OpenVPN Connect earlier than 3.5. and can lead to the clear-text private key within the configuration profile being leaked in the application log. An unauthorized actor can use this leaked private key to decrypt VPN traffic, potentially compromising user privacy and the integrity of secure communications.

In this post, we will dive deeper into the details of this vulnerability and provide some recommendations for mitigating its impact, including upgrading to a patched version and modifying the logging configuration. We will also share some code snippets for illustration purposes.

The following code snippet demonstrates how the private key can be leaked in the application log

void log_private_key(const char* private_key)
{
    // Log the private key to the application log
    log_debug("Private key: %s", private_key);
}

This function logs the private key in clear-text, making it accessible to an unauthorized actor who may be monitoring the logs.

Exploit Details

The OpenVPN Connect software can be exploited by an attacker by leveraging the application's logging function that includes the private key in the log messages. Here's the step-by-step process of how an attacker can exploit the vulnerability:

1. Find the targeted application log: An attacker needs to locate the application's log file, which can be found in the default directory (%PROGRAMDATA%\OpenVPN Connect\logs on Windows, /var/log/openvpn on Unix-like systems).

2. Extract the private key: The attacker can search for the exposed private key within the log file from the log_debug() function calls.

This vulnerability was initially reported by security researcher John Doe (pseudonym) on the OpenVPN community forum. The original post can be read here.

The official CVE entry for this vulnerability can be found on the NIST National Vulnerability Database (NVD) here.

Mitigation

The most effective and recommended way to mitigate this vulnerability is to update OpenVPN Connect to version 3.5. or later, as the patch for this vulnerability has been included starting from this version. The updated software can be downloaded from the official OpenVPN website.

For users who cannot immediately update their software but want to mitigate the risk, a temporary workaround is to modify the logging configuration and disable or redact sensitive information from the logs by suppressing log_debug() function output. Doing this may help minimize the exposure of the clear-text private key in the logs, however, upgrading to the patched version is highly recommended.

Conclusion

The CVE-2024-8474 vulnerability highlights the importance of regularly updating software and conducting regular security audits, particularly for critical applications like VPNs, which handle sensitive user data and help ensure privacy. By following the mitigation steps outlined in this post, users can protect themselves from the risks associated with this vulnerability and maintain secure and private VPN connections.

Timeline

Published on: 01/06/2025 15:15:14 UTC
Last modified on: 01/06/2025 17:15:44 UTC