OpenVPN Easy-rsa Vulnerability Allows Attacker to Bruteforce Private CA key

A significant security vulnerability, designated as CVE-2024-13454, has been discovered in the OpenVPN Easy-RSA tool, specifically affecting versions from 3.0.5 to 3.2.0 that utilize OpenSSL 3.

This flaw pertains to the incorrect encryption of password-protected Certificate Authority (CA) private keys when using the easyrsa build-ca command.

Instead of employing the secure aes-256-cbc cipher as intended, Easy-RSA incorrectly defaults to the outdated and less secure des-ede3-cbc cipher, leaving these critical keys vulnerable to brute-force attacks.

The implications of this vulnerability are severe, as it could potentially allow unauthorized users to compromise the CA private key, thereby undermining the integrity of the entire Public Key Infrastructure (PKI) built around it.

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Given the critical role CA private keys play in secure communications, organizations utilizing affected versions of Easy-RSA are urged to take immediate action.

To address this vulnerability, users should follow a two-pronged approach:

1. Re-encrypt the Private CA Key: Execute the command easyrsa set-pass ca to re-encrypt the CA private key using the recommended aes-256-cbc cipher algorithm. This command is functional across all Easy-RSA versions and will help mitigate the vulnerability.
2. Upgrade to a Secure Version: It is highly recommended that users upgrade to Easy-RSA version 3.2.0 or newer, where the cipher issue is rectified. This version not only uses the correct encryption method but also provides additional enhancements and security features.

Version-Specific Vulnerability Insights

According to the OpenVPN report, the vulnerability’s impact varies across different versions of Easy-RSA. Below is a summary of the encryption methods used in key commands:

• Easy-RSA 3.0.5 to 3.1.7: Utilizes des-ede3-cbc for build-ca, but switches to aes-256-cbc for set-pass.
• Easy-RSA 3.2.0 and later: Correctly uses aes-256-cbc for both build-ca and set-pass commands, addressing the vulnerability entirely.

Testing has shown that OpenSSL 1.x, specifically versions 1.1.0l and 1.1.1w, do not exhibit this issue, reinforcing the need for users on OpenSSL 3 to upgrade not only their Easy-RSA versions but also to reassess their dependency on OpenSSL versions.

The identification of CVE-2024-13454 highlights the importance of maintaining updated security practices and tools within the cybersecurity landscape.

Administrators and security teams should prioritize the recommended remediation steps to safeguard their infrastructures against potential exploits arising from this critical vulnerability.

Active engagement in vulnerability management will ensure a reliable and secure environment for digital communications.

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