CVE-2018-15481 in Wireless Appliance
Summary
by MITRE
Improper input sanitization within the restricted administration shell on UCOPIA Wireless Appliance devices using firmware version 5.1.x before 5.1.13 allows authenticated remote attackers to escape the shell and escalate their privileges by adding a LocalCommand to the SSH configuration file in the user home folder.
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Analysis
by VulDB Data Team • 03/17/2020
The vulnerability CVE-2018-15481 represents a critical security flaw in UCOPIA Wireless Appliance devices running firmware versions 5.1.x prior to 5.1.13. This issue resides within the restricted administration shell implementation, which is designed to limit administrative access and prevent unauthorized system manipulation. The vulnerability stems from inadequate input sanitization mechanisms that fail to properly validate and filter user-supplied data before processing within the shell environment. Attackers exploiting this weakness can leverage the restricted shell to execute arbitrary commands with elevated privileges, fundamentally undermining the security model of the device.
The technical exploitation of this vulnerability occurs through a specific attack vector involving SSH configuration file manipulation. An authenticated attacker with access to the restricted shell can add a LocalCommand directive to the SSH configuration file located in the user's home directory. This configuration directive allows arbitrary commands to be executed automatically when SSH connections are established, effectively bypassing the shell restrictions. The vulnerability is particularly dangerous because it leverages the legitimate SSH functionality to escalate privileges rather than exploiting a direct system vulnerability, making detection more challenging. This attack technique aligns with CWE-20, which describes improper input sanitization, and demonstrates how inadequate validation can lead to privilege escalation in restricted environments.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables attackers to gain full administrative control over the wireless appliance. This access can be used to modify network configurations, extract sensitive data, install malicious software, or establish persistent backdoors within the network infrastructure. The restricted shell environment, which is typically designed to prevent unauthorized access to critical system functions, becomes completely ineffective against this attack. Organizations relying on UCOPIA Wireless Appliances for network security may find their entire wireless infrastructure compromised, potentially affecting thousands of connected devices and creating significant attack surface expansion.
Mitigation strategies for CVE-2018-15481 should prioritize immediate firmware updates to version 5.1.13 or later, which contain the necessary patches to address the input sanitization issues. Network administrators should also implement additional security controls such as disabling unnecessary SSH features, monitoring SSH configuration file modifications, and conducting regular security audits of administrative access. The vulnerability demonstrates the importance of proper input validation in restricted environments and aligns with ATT&CK technique T1059.001 for command and scripting interpreter, as it enables execution of arbitrary commands through legitimate system interfaces. Organizations should also consider implementing network segmentation to limit the potential impact of such compromises and establish robust monitoring procedures to detect unauthorized configuration changes in SSH-related files.