CVE-2022-33738 in Access Server
Summary
by MITRE • 07/06/2022
OpenVPN Access Server before 2.11 uses a weak random generator used to create user session token for the web portal
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Analysis
by VulDB Data Team • 07/19/2022
The vulnerability identified as CVE-2022-33738 affects OpenVPN Access Server versions prior to 2.11, specifically targeting the web portal authentication mechanism through the use of a weak random number generator for session token creation. This flaw represents a critical security weakness that undermines the integrity of user sessions within the OpenVPN ecosystem. The vulnerability stems from the implementation of insufficient entropy sources during the generation of cryptographic tokens used to maintain user sessions, creating predictable and potentially exploitable session identifiers. The weakness directly impacts the authentication and authorization processes of the web portal interface, which serves as the primary administrative and user access point for the OpenVPN Access Server.
The technical implementation of this vulnerability involves the utilization of a pseudo-random number generator that lacks adequate cryptographic strength for generating session tokens. According to CWE-330, this represents a weakness in the use of weak random number generators where insufficient entropy leads to predictable outputs that can be exploited by attackers. The flaw creates opportunities for session hijacking attacks where malicious actors can predict or guess valid session tokens, thereby gaining unauthorized access to user sessions and potentially escalating privileges within the OpenVPN environment. The weak random generator typically employs algorithms with limited seed entropy or deterministic sequences that fail to meet cryptographic security requirements for session management.
From an operational impact perspective, this vulnerability creates significant risks for organizations relying on OpenVPN Access Server for remote access and network security. Attackers exploiting this weakness can perform session hijacking attacks, impersonate legitimate users, and potentially gain administrative access to the OpenVPN server configuration. The vulnerability affects both user authentication and administrative access through the web portal interface, creating a broad attack surface that could lead to complete compromise of the VPN infrastructure. The impact extends beyond simple unauthorized access to include potential data exfiltration, lateral movement within networks, and disruption of legitimate business operations that depend on secure remote access capabilities. Organizations using affected versions face increased risk of credential theft and unauthorized network access that could result in regulatory compliance violations and security breaches.
Mitigation strategies for CVE-2022-33738 primarily involve upgrading to OpenVPN Access Server version 2.11 or later, which implements proper cryptographic random number generation for session token creation. Organizations should also consider implementing additional security controls such as multi-factor authentication, network segmentation, and monitoring for suspicious session activity. The remediation aligns with ATT&CK technique T1566 which addresses credential harvesting through various methods including session hijacking and token prediction. Security teams should conduct comprehensive vulnerability assessments to identify all instances of affected OpenVPN Access Server installations and ensure proper patch management procedures are in place. Additionally, organizations should review their session management policies and implement monitoring solutions that can detect anomalous session behavior indicative of token prediction attacks. The vulnerability demonstrates the critical importance of cryptographic strength in session management and highlights the need for adherence to security standards such as NIST SP 800-90A for random number generation requirements in cryptographic applications.