CVE-2019-1939 in Webex Teams Client
Summary
by MITRE
A vulnerability in the Cisco Webex Teams client for Windows could allow an unauthenticated, remote attacker to execute arbitrary commands on an affected system. This vulnerability is due to improper restrictions on software logging features used by the application on Windows operating systems. An attacker could exploit this vulnerability by convincing a targeted user to visit a website designed to submit malicious input to the affected application. A successful exploit could allow the attacker to cause the application to modify files and execute arbitrary commands on the system with the privileges of the targeted user.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-1939 represents a critical security flaw in Cisco Webex Teams client for Windows operating systems. This issue stems from inadequate restrictions within the application's software logging features, creating an exploitable condition that can be leveraged by remote attackers without authentication. The vulnerability specifically affects the Windows implementation of the Webex Teams client, which is widely used for enterprise communication and collaboration purposes. The flaw demonstrates a classic example of improper input validation and output handling within client-side applications, where logging mechanisms become attack vectors rather than security controls. Organizations relying on Webex Teams for business communications face significant risk as this vulnerability can be exploited through social engineering techniques targeting end users.
The technical exploitation of CVE-2019-1939 occurs through a carefully crafted web-based attack vector that leverages the application's logging functionality. Attackers construct malicious websites designed to submit specially formatted input that triggers the vulnerable logging code path within the Windows client. When a targeted user visits such a malicious website, the application's logging features process the malicious input and inadvertently execute arbitrary code on the victim's system. The vulnerability essentially allows attackers to bypass normal application security boundaries and gain execution privileges equivalent to those of the targeted user. This type of attack aligns with attack patterns described in the ATT&CK framework under the technique of "Command and Scripting Interpreter" and "Exploitation for Client Execution" categories. The underlying flaw demonstrates poor input sanitization practices and inadequate validation of logging parameters, creating a path for code injection attacks that can escalate privileges within the user context.
The operational impact of this vulnerability extends beyond simple remote code execution, as it fundamentally undermines the security model of the Webex Teams client and potentially exposes enterprise networks to broader compromise. Since the attack requires only a user to visit a malicious website, it can be effectively delivered through phishing campaigns, drive-by downloads, or compromised websites that users might legitimately visit. The vulnerability affects organizations of all sizes as Webex Teams is widely adopted across enterprises, government agencies, and educational institutions. Successful exploitation can lead to persistent access, data exfiltration, lateral movement within networks, and potential escalation to system-level privileges depending on the user's access level. This vulnerability particularly impacts organizations with limited security awareness training, as the attack vector relies heavily on user interaction and social engineering rather than technical sophistication. The risk is compounded by the fact that the application runs with user privileges, meaning successful exploitation can provide attackers with access to user data, files, and potentially network resources accessible to that user account.
Organizations should implement immediate mitigations to address CVE-2019-1939, including prompt deployment of Cisco's security patches and updates to the Webex Teams client. System administrators should consider implementing network-based restrictions such as web filtering solutions to block access to known malicious domains and suspicious websites. The vulnerability's classification under CWE-20 (Improper Input Validation) and CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component) highlights the need for comprehensive code review processes and input validation mechanisms. Security teams should also enhance user awareness training programs to recognize potential phishing attempts and malicious websites that could exploit this vulnerability. Additional defensive measures include monitoring network traffic for suspicious patterns related to Webex Teams client communications and implementing application whitelisting policies where possible. The ATT&CK framework suggests organizations should also consider implementing behavioral analytics to detect anomalous application execution patterns that might indicate exploitation attempts. Regular vulnerability assessments and penetration testing should include evaluation of client-side applications and their logging mechanisms to identify similar security gaps that could be exploited by attackers.