CVE-2021-34423 in Client for Meetings
Summary
by MITRE • 11/24/2021
A buffer overflow vulnerability was discovered in Zoom Client for Meetings (for Android, iOS, Linux, macOS, and Windows) before version 5.8.4, Zoom Client for Meetings for Blackberry (for Android and iOS) before version 5.8.1, Zoom Client for Meetings for intune (for Android and iOS) before version 5.8.4, Zoom Client for Meetings for Chrome OS before version 5.0.1, Zoom Rooms for Conference Room (for Android, AndroidBali, macOS, and Windows) before version 5.8.3, Controllers for Zoom Rooms (for Android, iOS, and Windows) before version 5.8.3, Zoom VDI before version 5.8.4, Zoom Meeting SDK for Android before version 5.7.6.1922, Zoom Meeting SDK for iOS before version 5.7.6.1082, Zoom Meeting SDK for macOS before version 5.7.6.1340, Zoom Meeting SDK for Windows before version 5.7.6.1081, Zoom Video SDK (for Android, iOS, macOS, and Windows) before version 1.1.2, Zoom On-Premise Meeting Connector Controller before version 4.8.12.20211115, Zoom On-Premise Meeting Connector MMR before version 4.8.12.20211115, Zoom On-Premise Recording Connector before version 5.1.0.65.20211116, Zoom On-Premise Virtual Room Connector before version 4.4.7266.20211117, Zoom On-Premise Virtual Room Connector Load Balancer before version 2.5.5692.20211117, Zoom Hybrid Zproxy before version 1.0.1058.20211116, and Zoom Hybrid MMR before version 4.6.20211116.131_x86-64. This can potentially allow a malicious actor to crash the service or application, or leverage this vulnerability to execute arbitrary code.
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Analysis
by VulDB Data Team • 11/27/2021
This buffer overflow vulnerability in Zoom client applications represents a critical security flaw that affects multiple platform variants across the Zoom ecosystem. The vulnerability stems from improper input validation within the software's memory management routines, specifically when processing user-supplied data or network communications. According to CWE-121, this falls under the category of stack-based buffer overflow conditions where insufficient bounds checking allows attackers to write beyond allocated memory boundaries. The flaw exists across all major operating systems including android, ios, linux, macos, windows, and chrome os, indicating a systemic issue in the codebase rather than isolated platform-specific problems.
The technical implementation of this vulnerability allows malicious actors to manipulate memory structures through carefully crafted inputs that exceed buffer limits. When the application processes these oversized inputs, it can overwrite adjacent memory locations, potentially corrupting program execution flow or data structures. This type of vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation could enable arbitrary code execution, allowing attackers to gain full control over affected systems. The impact extends beyond simple service disruption to include complete system compromise, particularly when the vulnerable applications run with elevated privileges or access to sensitive network communications.
The operational implications of this vulnerability are severe given Zoom's widespread adoption in enterprise and educational environments. Attackers could leverage this flaw to gain persistent access to meeting systems, potentially intercepting sensitive communications or disrupting critical business operations. The vulnerability affects not only end-user clients but also the broader Zoom infrastructure including meeting connectors, virtual room connectors, and hybrid deployment components, creating a potential attack surface that spans multiple deployment models. Organizations using Zoom services for remote work, video conferencing, or hybrid meetings face significant risk of data breaches or service disruption. The vulnerability's presence across multiple versions and platforms suggests that attackers could target specific deployments based on their software versions, making it particularly dangerous in environments where patch management is inconsistent.
Mitigation strategies should focus on immediate patching of all affected versions to version 5.8.4 or later, depending on the specific product variant. Organizations should implement network monitoring to detect potential exploitation attempts, particularly focusing on unusual memory access patterns or network traffic originating from vulnerable clients. The principle of least privilege should be enforced by limiting the execution permissions of Zoom applications and ensuring they run with minimal required privileges. Additionally, network segmentation can help contain potential exploitation by isolating vulnerable systems from critical infrastructure. Security teams should also consider implementing application whitelisting policies that restrict execution of unauthorized Zoom components and monitor for unusual process behavior that might indicate exploitation attempts. Regular vulnerability assessments should be conducted to identify similar memory corruption issues in other enterprise applications, as this vulnerability demonstrates the importance of proper input validation and memory management in client-side applications.