Memory Leak in OpenVPN TLS-Crypt-V2 Client Key Extraction

Executive Summary

This vulnerability is a memory leak in OpenVPN versions 2.5.0 through 2.6.20 and 2.7_alpha1 through 2.7.4. It occurs during the tls-crypt-v2 client key extraction process. Remote attackers can exploit it by sending a large number of specially crafted packets, causing the system to exhaust memory resources.

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Detection Guidance

Detecting this vulnerability requires monitoring for memory exhaustion in OpenVPN processes. Check for high memory usage in OpenVPN servers or clients using system monitoring tools like top, htop, or ps commands. Look for processes named openvpn with unusually high memory consumption. You can also use netstat or ss commands to monitor network traffic patterns that may indicate crafted packet floods targeting the tls-crypt-v2 feature.

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Impact Analysis

The vulnerability can lead to a denial of service by consuming all available memory on the affected system. This may cause the OpenVPN service to crash or the entire system to slow down significantly, disrupting network operations and services relying on OpenVPN.

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Compliance Impact

This vulnerability causes memory exhaustion via crafted packets, leading to denial of service. It does not directly impact data confidentiality or integrity but may disrupt services handling sensitive data. Compliance impact depends on service availability requirements in standards like GDPR or HIPAA, where downtime could affect data processing obligations.

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Mitigation Strategies

Immediately upgrade OpenVPN to a patched version (2.6.21 or later, or 2.7.5 or later). If upgrading is not possible, disable the tls-crypt-v2 feature in your OpenVPN configuration files by removing or commenting out the tls-crypt-v2 directive. Implement rate limiting on network interfaces to prevent packet floods. Monitor system memory usage closely until patches are applied.

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