CVE-2018-13283 in SSL VPN Client
Summary
by MITRE
Lack of administrator control over security vulnerability in client.cgi in Synology SSL VPN Client before 1.2.5-0226 allows remote attackers to conduct man-in-the-middle attacks via the (1) command, (2) hostname, or (3) port parameter.
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Analysis
by VulDB Data Team • 08/21/2023
The vulnerability identified as CVE-2018-13283 affects Synology SSL VPN Client versions prior to 1.2.5-0226 and represents a critical security flaw in the client.cgi component that enables remote attackers to execute man-in-the-middle attacks. This issue stems from inadequate administrative control over security parameters within the SSL VPN client implementation, creating a significant attack surface that compromises the integrity of network communications. The vulnerability specifically targets three critical parameters including command, hostname, and port, which when manipulated by unauthorized parties can lead to complete compromise of the secure communication channel between clients and VPN servers.
The technical exploitation of this vulnerability occurs through the manipulation of input parameters within the client.cgi script, which fails to properly validate or sanitize user-supplied data. Attackers can inject malicious commands or redirect traffic to unauthorized endpoints by exploiting the lack of proper parameter validation mechanisms. This flaw aligns with CWE-20, which describes improper input validation, and represents a classic example of insecure parameter handling in web applications. The vulnerability allows adversaries to intercept, modify, or redirect network traffic without proper authentication or authorization, effectively breaking the cryptographic protections that SSL VPN services are designed to provide.
The operational impact of CVE-2018-13283 extends beyond simple data interception, as it enables attackers to establish persistent access points within corporate networks. When exploited successfully, this vulnerability allows threat actors to conduct comprehensive man-in-the-middle attacks that can capture sensitive credentials, decrypt network traffic, and potentially escalate privileges within the affected network infrastructure. Organizations using Synology SSL VPN clients in environments with sensitive data or critical infrastructure face significant risk, as the vulnerability can be leveraged to gain unauthorized access to internal systems without detection. The attack vector requires minimal technical expertise and can be automated, making it particularly dangerous for widespread deployment.
Mitigation strategies for this vulnerability require immediate implementation of the vendor-provided security update to version 1.2.5-0226 or later, which addresses the input validation issues in client.cgi. Network administrators should also implement additional security controls including mandatory certificate validation, network segmentation, and continuous monitoring of VPN traffic for anomalous patterns. The remediation process should include comprehensive testing of updated configurations to ensure that the vulnerability is fully resolved without introducing new issues. Organizations should also consider implementing network access controls and intrusion detection systems to detect potential exploitation attempts. This vulnerability demonstrates the critical importance of maintaining up-to-date security patches and proper input validation practices in network security applications, as highlighted by ATT&CK technique T1071.004 for application layer protocol tunneling and T1566 for credential harvesting through man-in-the-middle attacks.