CVE-2021-34412 in Client for Meetings
Summary
by MITRE • 09/27/2021
During the installation process for all versions of the Zoom Client for Meetings for Windows before 5.4.0, it is possible to launch Internet Explorer. If the installer was launched with elevated privileges such as by SCCM this can result in a local privilege escalation.
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Analysis
by VulDB Data Team • 10/02/2021
The vulnerability identified as CVE-2021-34412 represents a critical local privilege escalation flaw within the Zoom Client for Meetings Windows installation process. This issue affects all versions prior to 5.4.0 and stems from improper privilege handling during the installation procedure. The vulnerability specifically manifests when the Zoom installer executes with elevated privileges, such as those granted through enterprise deployment mechanisms like Microsoft System Center Configuration Manager. The core technical flaw occurs because the installer process fails to properly manage the execution context when launching Internet Explorer components during installation, creating an opportunity for privilege escalation.
The operational impact of this vulnerability extends significantly within enterprise environments where software deployment tools commonly execute installers with administrative privileges. When SCCM or similar deployment solutions invoke the Zoom installer, the elevated execution context can be leveraged to escalate privileges from standard user to system level access. This presents a substantial risk as attackers who gain access to a user account could potentially exploit this vulnerability to achieve system compromise. The vulnerability aligns with CWE-787, which describes out-of-bounds writes, and CWE-276, concerning insecure default permissions, as the installer fails to properly restrict execution contexts. From an ATT&CK framework perspective, this vulnerability maps to T1068, which covers privilege escalation through local exploits, and T1059, covering execution through Windows Command Shell.
The technical exploitation requires an attacker to first establish a foothold on a system where Zoom is installed or being deployed. Once the attacker has user-level access, they can trigger the vulnerable installation process through legitimate deployment channels, particularly when the installation is executed with elevated privileges. The vulnerability essentially creates a privilege escalation pathway where the installer's elevated context can be used to execute arbitrary code with system-level privileges. Security professionals should note that this vulnerability is particularly dangerous in environments where automated deployment systems are used, as the escalation can occur without user interaction. Organizations should prioritize immediate patching to version 5.4.0 or later, as this update addresses the privilege escalation mechanism within the installation process. Additionally, implementing least privilege principles for deployment tools and monitoring for unusual installation activity can help detect potential exploitation attempts. The vulnerability underscores the importance of proper privilege separation in installation processes and demonstrates how seemingly benign components like Internet Explorer launch can create significant security risks when executed with elevated privileges.