CVE-2018-0422 in Webex Meetings Client
Summary
by MITRE
A vulnerability in the folder permissions of Cisco Webex Meetings client for Windows could allow an authenticated, local attacker to modify locally stored files and execute code on a targeted device with the privilege level of the user. The vulnerability is due to folder permissions that grant a user the permission to read, write, and execute files in the Webex folders. An attacker could exploit this vulnerability to write malicious files to the Webex client directory, affecting all other users of the targeted device. A successful exploit could allow a user to execute commands with elevated privileges. Attacks on single-user systems are less likely to occur, as the attack must be carried out by the user on the user's own system. Multiuser systems have a higher risk of exploitation because folder permissions have an impact on all users of the device. For an attacker to exploit this vulnerability successfully, a second user must execute the locally installed malicious file to allow remote code execution to occur.
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Analysis
by VulDB Data Team • 05/22/2023
The vulnerability identified as CVE-2018-0422 represents a critical privilege escalation flaw within the Cisco Webex Meetings client for Windows operating systems. This issue stems from improper folder permissions that grant excessive access controls to the Webex client installation directories, creating a persistent security weakness that can be exploited by authenticated local attackers. The vulnerability specifically affects the Windows client implementation of Cisco Webex Meetings, where the application's installation folder structure contains permissions that allow any user account on the system to read, write, and execute files within the Webex directory tree. This misconfiguration creates a fundamental security flaw in the application's access control model, as the permissions are not properly restricted to prevent unauthorized modifications to critical application components.
The technical exploitation of this vulnerability requires an attacker to first authenticate to the system with a valid user account, as the flaw does not permit arbitrary code execution without local access. Once authenticated, the attacker can leverage the overly permissive folder permissions to inject malicious code into the Webex client installation directory, effectively creating a persistent backdoor that can be executed by other users who subsequently run the Webex application. The attack vector specifically targets the local file system permissions rather than network-based vulnerabilities, making it a local privilege escalation issue that operates at the operating system level. This type of vulnerability aligns with CWE-276, which describes improper file permissions, and represents a classic case of insufficient access control in application installations.
The operational impact of CVE-2018-0422 extends significantly beyond simple local code execution, as it can affect all users of a multi-user system where the Webex client is installed. On single-user systems, the exploitation risk is reduced since the attacker must be the legitimate user of the system, but on multi-user environments such as shared workstations, terminal servers, or corporate devices, the vulnerability becomes much more dangerous. The attack requires a two-step process where the malicious file must first be written to the Webex directory by one user, and then executed by another user who runs the Webex client application. This execution model creates a scenario where a compromised user account can potentially affect the entire system's security posture, as any user who subsequently launches Webex could inadvertently execute the attacker's malicious payload.
The risk assessment for this vulnerability demonstrates a medium to high severity classification from a cybersecurity perspective, particularly in enterprise environments where multi-user systems are common. The vulnerability's impact is amplified by its potential for privilege escalation, as successful exploitation could allow attackers to execute commands with the privileges of the Webex client user account, which may have elevated system access rights. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the 'Permission Groups' and 'File and Directory Permissions Modification' tactics. Organizations using Cisco Webex Meetings client on Windows systems face a significant risk of persistent security compromise, as the vulnerability creates a foothold that can be maintained across system reboots and user sessions. The vulnerability affects systems where Webex is installed with default permissions, making it particularly concerning for organizations that do not regularly audit their application installation permissions and access controls.
Mitigation strategies for CVE-2018-0422 should focus on immediate permission adjustments to the Webex client installation directories, ensuring that only authorized system administrators have write and execute permissions. System administrators should implement regular security audits of application installations and verify that folder permissions follow the principle of least privilege. The recommended approach includes modifying the Windows file permissions for the Webex installation directories to restrict write access to the SYSTEM account and authorized administrators only. Additionally, organizations should consider implementing application whitelisting solutions that can prevent unauthorized executable files from running in the Webex directory. The vulnerability highlights the importance of proper application security hardening practices and demonstrates how seemingly minor permission misconfigurations can create significant security risks. Regular patch management procedures should also be implemented to ensure that Cisco releases security updates addressing this specific permission flaw, as the vulnerability represents a design weakness in the application's installation and access control model that requires both immediate remediation and long-term architectural considerations.