CVE-2021-34409 in Client for Meetings
Summary
by MITRE • 09/27/2021
User-writable pre and post-install scripts unpacked during the Zoom Client for Meetings for MacOS installation before version 5.2.0 allow for privilege escalation to root.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/02/2021
The vulnerability identified as CVE-2021-34409 represents a critical privilege escalation flaw within the Zoom Client for Meetings installation process on macOS systems. This issue affects versions prior to 5.2.0 and stems from the improper handling of pre and post-installation scripts during the software deployment phase. The core technical flaw occurs when the installer unpacks user-writable script files that are executed with elevated privileges, creating an exploitable condition where malicious actors can inject arbitrary code into these scripts before installation completion. The vulnerability aligns with CWE-787, representing an out-of-bounds write condition that allows unauthorized code execution with root privileges.
During the Zoom Client installation on macOS, the installer process creates and executes pre and post-installation scripts that are designed to configure the application environment and perform system-level modifications. The flaw emerges because these scripts are stored in locations where regular users possess write permissions, enabling them to modify the scripts before execution. When the installer subsequently runs these modified scripts with root privileges, the malicious code executes with elevated permissions, effectively granting attackers complete system control. This vulnerability directly maps to ATT&CK technique T1068, which covers privilege escalation through local exploitation of software vulnerabilities.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete system compromise capabilities. Once an attacker successfully exploits this vulnerability, they can modify system files, install persistent backdoors, access sensitive data, and establish covert communication channels. The attack vector is particularly concerning because it requires no special privileges to initiate the exploitation process, making it accessible to any user with local access to the target system. The vulnerability's exploitation potential is further amplified by the widespread adoption of Zoom Client for Meetings, creating a large attack surface across enterprise and personal computing environments.
Mitigation strategies for CVE-2021-34409 should prioritize immediate patching of affected systems to version 5.2.0 or later, which addresses the script execution privilege issue. Organizations should implement strict file permission controls on installation directories and monitor for unauthorized modifications to script files during installation processes. System administrators should also consider implementing application whitelisting policies to restrict execution of unknown or untrusted installation packages. The remediation approach aligns with security best practices outlined in NIST SP 800-171 and ISO 27001 standards, particularly regarding access control and system integrity protection measures. Additionally, regular security audits should verify that installation scripts are properly secured and that no user-writable components exist in privileged execution paths.