CVE-2019-1816 in Web Security Appliance
Summary
by MITRE
A vulnerability in the log subscription subsystem of the Cisco Web Security Appliance (WSA) could allow an authenticated, local attacker to perform command injection and elevate privileges to root. The vulnerability is due to insufficient validation of user-supplied input on the web and command-line interface. 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 • 09/12/2023
The Cisco Web Security Appliance WSA log subscription subsystem contains a critical command injection vulnerability that enables authenticated local attackers to escalate privileges to root access. This vulnerability resides in the insufficient validation of user-supplied input across both web and command-line interfaces, creating a pathway for malicious command execution. The flaw represents a significant security weakness in the appliance's input handling mechanisms, where properly crafted payloads can bypass validation checks and be executed within the system's operational context.
The technical exploitation of CVE-2019-1816 leverages the inadequate sanitization of input parameters within the log subscription functionality. When an authenticated user submits malicious input through either the web interface or command-line interface, the system fails to properly validate or escape the supplied data before processing it within the log subscription subsystem. This vulnerability maps directly to CWE-77 which describes improper neutralization of special elements used in a command, and CWE-20 which addresses input validation issues. The attack vector requires local authentication access to the device, making it particularly dangerous in environments where administrative credentials might be compromised or where insider threats exist.
Operational impact of this vulnerability extends beyond simple command execution to full system compromise through privilege escalation. An attacker who successfully exploits this vulnerability can execute arbitrary commands with root privileges, effectively gaining complete control over the appliance's operating system. This level of access enables attackers to modify system configurations, install malware, exfiltrate sensitive data, or establish persistent backdoors. The vulnerability undermines the appliance's primary security function as a web security gateway, potentially allowing attackers to bypass all security controls implemented by the device and access protected network resources.
Mitigation strategies for CVE-2019-1816 should include immediate deployment of Cisco's official security patches and updates. Organizations must implement strict access controls and limit local administrative access to only trusted personnel who require such privileges for legitimate maintenance purposes. Network segmentation and monitoring should be enhanced to detect anomalous command execution patterns that might indicate exploitation attempts. The principle of least privilege should be enforced across all administrative interfaces, with regular audit trails maintained to track user activities. Additionally, security teams should implement intrusion detection systems capable of identifying command injection attempts and establish comprehensive incident response procedures for rapid remediation of compromised systems. This vulnerability demonstrates the critical importance of input validation in security-critical subsystems and aligns with ATT&CK technique T1059 for command and scripting interpreter, specifically targeting the execution of arbitrary commands through vulnerable interfaces.