CVE-2023-5593 in SecuExtender SSL VPN Client
Summary
by MITRE • 11/20/2023
The out-of-bounds write vulnerability in the Windows-based SecuExtender SSL VPN Client software version 4.0.4.0 could allow an authenticated local user to gain a privilege escalation by sending a crafted CREATE message.
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Analysis
by VulDB Data Team • 11/20/2023
The vulnerability identified as CVE-2023-5593 represents a critical out-of-bounds write flaw within the SecuExtender SSL VPN Client software running on Windows platforms. This security weakness specifically affects version 4.0.4.0 of the client software and stems from inadequate input validation mechanisms within the application's processing of CREATE messages. The vulnerability manifests when an authenticated local user exploits a flaw in the memory management routines that handle incoming network communications, potentially allowing arbitrary code execution with elevated privileges.
The technical nature of this vulnerability aligns with CWE-787, which describes out-of-bounds write conditions where a program writes data past the end of a buffer or array. This particular flaw occurs during the processing of CREATE messages that are part of the VPN client's communication protocol, suggesting that the software fails to properly validate the length or content of incoming message structures before attempting to write to allocated memory regions. The out-of-bounds write condition creates a potential privilege escalation vector because the affected software operates with elevated privileges necessary for VPN functionality, making successful exploitation particularly dangerous.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on SecuExtender SSL VPN services, as it requires only local authentication to exploit. The authenticated local user context means that an attacker who has already compromised a user account or gained local access to a system running the vulnerable client can leverage this flaw to escalate their privileges to system level access. This scenario aligns with ATT&CK technique T1068, which covers local privilege escalation through exploitation of software vulnerabilities, and T1566, which encompasses initial access via valid accounts. The impact extends beyond individual system compromise as successful exploitation could enable attackers to establish persistent access to the organization's network infrastructure.
The exploitation of this vulnerability could enable attackers to execute arbitrary code with SYSTEM privileges, potentially allowing them to install malware, modify system configurations, or establish backdoors. The fact that this vulnerability affects the VPN client software means that organizations may be exposed across multiple endpoints where the client is installed, creating a widespread attack surface. Security professionals should consider this vulnerability in the context of broader network security strategies, particularly when evaluating the risk of lateral movement and persistent threats within corporate networks that rely heavily on VPN connectivity.
Organizations should prioritize immediate remediation through official vendor patches or updates, as the vulnerability's local authentication requirement does not necessarily prevent exploitation in environments where attackers have already compromised user accounts. The mitigation strategy should include comprehensive vulnerability scanning to identify all systems running the affected software version, along with network monitoring to detect potential exploitation attempts. Additionally, implementing principle of least privilege controls and maintaining up-to-date security patches across all VPN client installations will help reduce the risk of successful exploitation. The vulnerability's classification as a privilege escalation issue underscores the importance of maintaining secure configurations and monitoring for unauthorized access attempts within VPN environments.