CVE-2018-0428 in Web Security Appliance
Summary
by MITRE
A vulnerability in the account management subsystem of Cisco Web Security Appliance (WSA) could allow an authenticated, local attacker to elevate privileges to root. The attacker must authenticate with valid administrator credentials. The vulnerability is due to improper implementation of access controls. An attacker could exploit this vulnerability by authenticating to the device as a specific user to gain the information needed to elevate privileges to root in a separate login shell. A successful exploit could allow the attacker to escape the CLI subshell and execute system-level commands on the underlying operating system as root. Cisco Bug IDs: CSCvj93548.
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Analysis
by VulDB Data Team • 05/02/2023
The vulnerability identified as CVE-2018-0428 resides within the account management subsystem of Cisco Web Security Appliance WSA devices, representing a critical privilege escalation flaw that undermines the security posture of these network protection systems. This vulnerability specifically targets the authentication and authorization mechanisms that govern administrative access to the appliance, creating a pathway for authenticated attackers to escalate their privileges from administrator level to full root access. The flaw manifests through inadequate implementation of access controls that should normally prevent users from gaining unauthorized system-level privileges, thereby violating fundamental security principles of least privilege and privilege separation. The vulnerability affects Cisco WSA devices running specific software versions where the access control implementation fails to properly validate and enforce privilege boundaries between different user roles and system functions. The attack vector requires an initial authenticated session with valid administrator credentials, making this a local privilege escalation vulnerability that operates within the context of legitimate administrative access but exploits design flaws in the privilege management system.
The technical implementation of this vulnerability stems from improper access control mechanisms that fail to adequately separate user sessions and privilege levels within the WSA's command-line interface environment. When an authenticated administrator logs into the device, the system does not properly enforce boundaries between the administrative shell and the underlying operating system, allowing a malicious user to manipulate session contexts or exploit specific command execution pathways that lead to root privilege escalation. The vulnerability specifically enables attackers to escape from the constrained command-line interface subshell into the full operating system shell, where they can execute arbitrary system-level commands with the highest possible privileges. This occurs due to insufficient input validation and privilege boundary enforcement mechanisms that should normally prevent users from accessing underlying system functions. The exploitation process involves leveraging the initial administrative session to gather information or execute specific commands that manipulate the session state, ultimately enabling the attacker to obtain root-level access through a separate login shell. This type of vulnerability aligns with CWE-284, which addresses improper access control in software implementations, and demonstrates how inadequate privilege management can create pathways for unauthorized system-level access.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete control over the affected WSA appliance and its underlying operating system. Once escalated to root privileges, attackers can modify system configurations, access all stored data including proxy logs and security policies, install malicious software, or even compromise the entire network infrastructure protected by the appliance. The vulnerability undermines the integrity and confidentiality of the security appliance itself, potentially allowing attackers to bypass all security controls implemented by the device and gain access to sensitive network traffic and user data. Network administrators may be unaware of the compromise since the attack occurs through legitimate administrative sessions, making detection particularly challenging. The exploitation capability also enables attackers to potentially use the compromised appliance as a pivot point for further attacks within the network, leveraging the appliance's position as a security gateway to access other systems. This vulnerability represents a significant threat to network security operations, as it allows attackers to subvert the very security mechanisms designed to protect the network infrastructure.
Mitigation strategies for CVE-2018-0428 should focus on both immediate remediation and long-term security hardening measures. Cisco has released software updates and patches to address this vulnerability, which should be applied immediately to all affected WSA appliances. Organizations should implement strict access control policies limiting administrative access to only essential personnel with valid business justification, while also employing multi-factor authentication where possible to add additional layers of security. Network segmentation and monitoring should be enhanced to detect unusual administrative activities that might indicate privilege escalation attempts. Regular security assessments and vulnerability scanning should include checks for similar access control flaws in other network security devices. The implementation of principle of least privilege should be enforced more rigorously, ensuring that administrative accounts have only the minimum permissions necessary for their specific functions. Additionally, organizations should consider implementing behavioral analytics and anomaly detection systems that can identify suspicious patterns of administrative activity that may indicate exploitation attempts. This vulnerability highlights the importance of proper access control implementation and demonstrates how seemingly minor flaws in privilege management can create significant security risks that compromise entire network security infrastructures. The attack pattern aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and emphasizes the need for robust access control mechanisms in network security appliances.