How severe is CVE-2021-34423?

CVE-2021-34423 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-34423 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34423?

CVE-2021-34423 primarily affects Zoom Meetings. In total, 26 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-34423?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-34423 published?

CVE-2021-34423 was published on 2021-11-24 and last updated on 2026-06-17.

CVE-2021-34423

CVE-2021-34423 is a critical-severity vulnerability in Zoom Meetings with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (87th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Zoom Meetings
Published: 2021-11-24
Last modified: 2026-06-17

Description

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 Windows Meeting Client before version 5.8.4, Zoom VDI Azure Virtual Desktop Plugins (for Windows x86 or x64, IGEL x64, Ubuntu x64, HP ThinPro OS x64) before version 5.8.4.21112, Zoom VDI Citrix Plugins (for Windows x86 or x64, Mac Universal Installer & Uninstaller, IGEL x64, eLux RP6 x64, HP ThinPro OS x64, Ubuntu x64, CentOS x 64, Dell ThinOS) before version 5.8.4.21112, Zoom VDI VMware Plugins (for Windows x86 or x64, Mac Universal Installer & Uninstaller, IGEL x64, eLux RP6 x64, HP ThinPro OS x64, Ubuntu x64, CentOS x 64, Dell ThinOS) before version 5.8.4.21112, 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.

Frequently asked questions

What is CVE-2021-34423?: 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 Windows Meeting Client before version 5.8.4, Zoom VDI Azure Virtual Desktop Plugins (for Windows x86 or x64, IGEL x64, Ubuntu x64, HP ThinPro OS x64) before version 5.8.4.21112, Zoom VDI Citrix Plugins (for Windows x86 or x64, Mac Universal Installer & Uninstaller, IGEL x64, eLux RP6 x64, HP ThinPro OS x64, Ubuntu x64, CentOS x 64, Dell ThinOS) before version 5.8.4.21112, Zoom VDI VMware Plugins (for Windows x86 or x64, Mac Universal Installer & Uninstaller, IGEL x64, eLux RP6 x64, HP ThinPro OS x64, Ubuntu x64, CentOS x 64, Dell ThinOS) before version 5.8.4.21112, 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.
How severe is CVE-2021-34423?: CVE-2021-34423 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-34423 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34423?: CVE-2021-34423 primarily affects Zoom Meetings. In total, 26 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-34423?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-34423 published?: CVE-2021-34423 was published on 2021-11-24 and last updated on 2026-06-17.

References

Affected products (26)

cpe:2.3:a:zoom:meetings:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:meetings_for_blackberry:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:meetings_for_intune:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:meetings_for_chrome_os:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:rooms_for_conference_rooms:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:controllers_for_zoom_rooms:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:virtual_desktop_infrastructure:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:android_meeting_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:iphone_os_meeting_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:macos_meeting_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:windows_meeting_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:android_video_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:iphone_os_video_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:macos_video_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:windows_video_sdk:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:hybrid_mmr:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:hybrid_zproxy:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:zoom_on-premise_meeting_connector_controller:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:zoom_on-premise_meeting_connector_mmr:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:zoom_on-premise_recording_connector:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:zoom_on-premise_virtual_room_connector:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:zoom_on-premise_virtual_room_connector_load_balancer:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:vdi_azure_virtual_desktop:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:vdi_citrix:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:vdi_vmware:*:*:*:*:*:*:*:*
cpe:2.3:a:zoom:vdi_windows_meeting_client:*:*:*:*:*:*:*:*

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