CVE-2020-3367 in Secure Web Appliance
Summary
by MITRE • 11/18/2020
A vulnerability in the log subscription subsystem of Cisco AsyncOS for the Cisco Secure Web Appliance (formerly Web Security Appliance) could allow an authenticated, local attacker to perform command injection and elevate privileges to root. This vulnerability is due to insufficient validation of user-supplied input for the web interface and CLI. An attacker could exploit this vulnerability by authenticating to the affected device and injecting scripting commands in the scope of the log subscription subsystem. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system and elevate privileges to root.
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Analysis
by VulDB Data Team • 12/08/2020
The vulnerability identified as CVE-2020-3367 resides within the log subscription subsystem of Cisco AsyncOS for the Cisco Secure Web Appliance, formerly known as the Web Security Appliance. This critical flaw represents a command injection vulnerability that specifically targets the device's web interface and command-line interface components. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data before processing within the log subscription functionality. Attackers exploiting this weakness can leverage authenticated access to inject malicious scripts that execute with elevated privileges, ultimately achieving root-level system compromise.
The technical exploitation of this vulnerability follows a well-defined pattern that aligns with common command injection attack methodologies. The insufficient validation of user input creates a pathway for attackers to manipulate the log subscription subsystem through carefully crafted commands that bypass normal security controls. This flaw operates at the intersection of multiple security domains, combining elements of privilege escalation and command injection that can be classified under CWE-77 and CWE-78 within the Common Weakness Enumeration framework. The vulnerability's impact is amplified by its local nature, requiring only authentication to the device rather than remote access, making it particularly dangerous in environments where physical or administrative access is possible.
From an operational perspective, the consequences of successful exploitation extend far beyond simple privilege escalation. The ability to execute arbitrary commands on the underlying operating system provides attackers with complete control over the affected appliance, potentially enabling them to modify system configurations, extract sensitive data, or establish persistent access points. This vulnerability directly impacts the integrity and availability of the web security appliance, which serves as a critical component in network security infrastructure. The attack vector leverages the legitimate administrative interfaces of the device, making detection more challenging as malicious activities can appear as normal administrative operations within system logs.
The security implications of CVE-2020-3367 align with several techniques documented in the MITRE ATT&CK framework, particularly those related to privilege escalation and command execution. The vulnerability creates opportunities for attackers to move laterally within networks where the appliance serves as a security gateway, potentially compromising other systems that trust the appliance's security posture. Organizations implementing the Cisco Secure Web Appliance must consider this vulnerability as part of their broader security assessment, particularly in environments where administrative access controls may be insufficient or where the appliance serves as a critical network boundary device. The vulnerability's classification as a local privilege escalation issue means that even limited administrative access can be leveraged to achieve complete system compromise.
Mitigation strategies for CVE-2020-3367 should focus on immediate patching of affected devices through Cisco's security advisories and firmware updates. Organizations should implement strict access controls limiting authentication to the web interface and CLI to only authorized personnel with legitimate administrative needs. Network segmentation and monitoring of administrative activities can help detect anomalous behavior that might indicate exploitation attempts. The implementation of principle of least privilege should extend to administrative accounts, ensuring that users have only the minimum permissions required for their specific roles. Regular security assessments and vulnerability scanning should include verification of patch status for the affected subsystems, as this vulnerability represents a persistent risk that requires ongoing monitoring and remediation efforts to maintain system integrity.