Critical OpenVPN Vulnerabilities Expose Systems to Attacks
OpenVPN, a widely utilized open-source VPN solution, has recently addressed several critical vulnerabilities that could have allowed attackers to disrupt services, bypass security measures, and access sensitive information. These issues, affecting both stable and development versions, underscore the importance of timely software updates to maintain system security.
Windows Interactive Service Denial-of-Service (CVE-2025-13751):
A significant flaw was identified in OpenVPN’s Windows interactive service component, designated as CVE-2025-13751. This vulnerability could enable authenticated local users to trigger a denial-of-service (DoS) condition by exploiting an erroneous exit routine. Specifically, the service would terminate upon encountering certain error conditions, halting all VPN connections until manual intervention. This issue affected OpenVPN versions 2.6.0 through 2.6.16 and 2.7_alpha1 through 2.7_rc2. The problem has been rectified in versions 2.6.17 and 2.7_rc3.
HMAC Verification Bypass (CVE-2025-13086):
Another critical vulnerability, CVE-2025-13086, involved a logic flaw in the HMAC verification process during the three-way handshake. Due to an inverted comparison function, the system inadvertently accepted all HMAC cookies, effectively nullifying source IP address validation. This oversight allowed attackers to bypass initial verification layers, potentially initiating unauthorized TLS sessions and consuming server resources. The vulnerability was present in versions 2.6.0 through 2.6.15 and has been addressed in version 2.6.16.
IPv6 Buffer Over-Read (CVE-2025-12106):
In the development branch, a high-severity memory safety issue, CVE-2025-12106, was discovered. This flaw resulted from a mismatched address family check in the get_addr_generic function, leading to a heap buffer over-read when parsing invalid IPv6 input. While this vulnerability had the potential for memory corruption, it was limited to versions 2.7_alpha1 through 2.7_rc1 and did not affect the stable 2.6 branch. The issue has been resolved in version 2.7_rc2.
OpenVPN Connect Private Key Exposure (CVE-2024-8474):
A critical vulnerability, CVE-2024-8474, was identified in OpenVPN Connect, the client software for OpenVPN. This flaw involved improper handling of sensitive information, where the application logged private keys from configuration profiles in clear text within its logs. Unauthorized access to these logs could allow attackers to retrieve private keys, potentially decrypting intercepted VPN traffic and compromising secure communications. This issue affected all versions of OpenVPN Connect prior to 3.5.0 and has been addressed in the latest release.
OpenVPN Easy-RSA Weak Encryption Vulnerability (CVE-2024-13454):
In Easy-RSA, a utility for managing Public Key Infrastructure (PKI) for OpenVPN, a vulnerability identified as CVE-2024-13454 was discovered. This flaw allowed private Certificate Authority (CA) keys to be encrypted using the outdated and weak cipher DES-EDE3-CBC (3DES), making them susceptible to brute-force attacks. The vulnerability affected Easy-RSA versions 3.0.5 through 3.1.7 when used with OpenSSL 3. Users are advised to update to the latest version to mitigate this risk.
OpenVPN Driver Vulnerability on Windows (CVE-2025-50054):
A critical buffer overflow vulnerability, CVE-2025-50054, was found in OpenVPN’s data channel offload driver for Windows. This flaw allowed local attackers to crash Windows systems by sending maliciously crafted control messages. The vulnerability affected the ovpn-dco-win driver versions 1.3.0 and earlier, as well as version 2.5.8 and earlier. OpenVPN has released version 2.7_alpha2 to address this issue, and users are encouraged to update promptly.
Mitigation Steps:
To protect systems from these vulnerabilities, users and administrators should:
– Update OpenVPN Software: Ensure that OpenVPN installations are updated to the latest versions (2.6.17 for stable releases and 2.7_rc3 for development releases) to incorporate security patches.
– Review and Secure Logs: Regularly audit application logs to prevent unauthorized access to sensitive information.
– Implement Strong Access Controls: Limit access to devices running OpenVPN and enforce robust authentication mechanisms.
– Monitor Network Activity: Continuously observe for unusual activities and ensure endpoint security measures are up to date.
By proactively addressing these vulnerabilities and adhering to best security practices, organizations can maintain the integrity and confidentiality of their VPN communications.
