CVE-2020-11632 in Client Connector
Summary
by MITRE • 07/16/2021
The Zscaler Client Connector prior to 2.1.2.150 did not quote the search path for services, which allows a local adversary to execute code with system privileges.
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Analysis
by VulDB Data Team • 07/19/2021
The vulnerability identified as CVE-2020-11632 affects the Zscaler Client Connector software version 2.1.2.149 and earlier, representing a critical privilege escalation flaw that stems from improper handling of service search paths. This issue creates a dangerous condition where malicious actors can manipulate the system's service resolution mechanism to execute arbitrary code with elevated system privileges. The root cause lies in the software's failure to properly quote or sanitize the search paths used by Windows services, a fundamental security oversight that directly enables path traversal attacks.
This vulnerability operates through a classic path injection attack vector where an attacker can place a malicious executable in a location that gets searched before the legitimate service binary. The Zscaler Client Connector, when running with system privileges, processes service paths without proper quoting mechanisms that would prevent the operating system from searching in unintended directories. This behavior aligns with CWE-428, which describes the improper neutralization of special elements used in an OS command, and more specifically with CWE-78, the improper neutralization of special elements used in a command, both of which are foundational to command injection vulnerabilities. The flaw essentially allows attackers to hijack the service execution flow by placing malicious binaries in directories that are searched before the intended service locations.
The operational impact of this vulnerability is severe and directly enables local privilege escalation attacks that can result in complete system compromise. An attacker with local access can exploit this weakness to execute code with SYSTEM privileges, potentially gaining access to all system resources, user data, and network communications. This vulnerability is particularly dangerous in enterprise environments where Zscaler Client Connector is widely deployed, as it can be leveraged to establish persistent backdoors, exfiltrate sensitive data, or escalate privileges to gain administrative control over network infrastructure. The attack surface is broad since many organizations rely on Zscaler for network security, making this a valuable target for adversaries seeking to maintain long-term access to corporate networks.
Mitigation strategies for CVE-2020-11632 focus primarily on immediate software updates to version 2.1.2.150 or later, which properly implements quoted search paths for service execution. System administrators should also implement additional security controls including regular security audits of service configurations, monitoring for unauthorized binary installations in system directories, and implementing least privilege principles for service accounts. The vulnerability demonstrates the importance of proper input validation and path handling in service management, aligning with ATT&CK technique T1068, which covers the use of privilege escalation techniques through service execution. Organizations should also consider implementing application control measures such as Windows Defender Application Control or similar technologies to prevent execution of unauthorized binaries, and should conduct thorough vulnerability assessments to identify any other applications suffering from similar path handling issues. The remediation process should include comprehensive testing to ensure that the update does not introduce compatibility issues with existing network security policies or configurations.