CriticalCVE-2021-34423

    Buffer overflow in Zoom client and other products (CVE-2021-34423)

    Published Sources: CVE.org

    What is affected, what to do

    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.

    An exploit is publicly available. Update Zoom Client for Meetings (for Android, iOS, Linux, macOS, and Windows) to version 5.8.4, Zoom Client for Meetings for Blackberry (for Android and iOS) to version 5.8.1, Zoom Client for Meetings for intune (for Android and iOS) to version 5.8.4.

    Affected
    • Zoom Client for Meetings (for Android, iOS, Linux, macOS, and Windows) lt *..5.8.4
    • Zoom Client for Meetings for Blackberry (for Android and iOS) lt *..5.8.1
    • Zoom Client for Meetings for intune (for Android and iOS) lt *..5.8.4
    • Zoom Client for Meetings for Chrome OS lt *..5.0.1
    • Zoom Rooms for Conference Room (for Android, AndroidBali, macOS, and Windows) lt *..5.8.3
    • Zoom Video Communications Controllers for Zoom Rooms (for Android, iOS, and Windows) lt *..5.8.3
    • Zoom VDI Windows Meeting Client lt *..5.8.4
    • Zoom VDI Azure Virtual Desktop Plugins (for Windows x86 or x64, IGEL x64, Ubuntu x64, HP ThinPro OS x64) lt *..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) lt *..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) lt *..5.8.4.21112
    • Zoom Meeting SDK for Android lt *..5.7.6.1922
    • Zoom Meeting SDK for iOS lt *..5.7.6.1082
    • Zoom Meeting SDK for macOS lt *..5.7.6.1340
    • Zoom Meeting SDK for Windows lt *..5.7.6.1081
    • Zoom Video SDK (for Android, iOS, macOS, and Windows) lt *..1.1.2
    • Zoom On-Premise Meeting Connector Controller lt *..4.8.12.20211115
    • Zoom On-Premise Meeting Connector MMR lt *..4.8.12.20211115
    • Zoom On-Premise Recording Connector lt *..5.1.0.65.20211116
    • Zoom On-Premise Virtual Room Connector lt *..4.4.7266.20211117
    • Zoom On-Premise Virtual Room Connector Load Balancer lt *..2.5.5692.20211117
    • Zoom Hybrid Zproxy lt *..1.0.1058.20211116
    • Zoom Hybrid MMR lt *..4.6.20211116.131_x86-64
    Fixed in
    • Zoom Client for Meetings (for Android, iOS, Linux, macOS, and Windows) 5.8.4
    • Zoom Client for Meetings for Blackberry (for Android and iOS) 5.8.1
    • Zoom Client for Meetings for intune (for Android and iOS) 5.8.4
    • Zoom Client for Meetings for Chrome OS 5.0.1
    • Zoom Rooms for Conference Room (for Android, AndroidBali, macOS, and Windows) 5.8.3
    • Zoom Video Communications Controllers for Zoom Rooms (for Android, iOS, and Windows) 5.8.3
    • Zoom VDI Windows Meeting Client 5.8.4
    • Zoom VDI Azure Virtual Desktop Plugins (for Windows x86 or x64, IGEL x64, Ubuntu x64, HP ThinPro OS x64) 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) 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) 5.8.4.21112
    • Zoom Meeting SDK for Android 5.7.6.1922
    • Zoom Meeting SDK for iOS 5.7.6.1082
    • Zoom Meeting SDK for macOS 5.7.6.1340
    • Zoom Meeting SDK for Windows 5.7.6.1081
    • Zoom Video SDK (for Android, iOS, macOS, and Windows) 1.1.2
    • Zoom On-Premise Meeting Connector Controller 4.8.12.20211115
    • Zoom On-Premise Meeting Connector MMR 4.8.12.20211115
    • Zoom On-Premise Recording Connector 5.1.0.65.20211116
    • Zoom On-Premise Virtual Room Connector 4.4.7266.20211117
    • Zoom On-Premise Virtual Room Connector Load Balancer 2.5.5692.20211117
    • Zoom Hybrid Zproxy 1.0.1058.20211116
    • Zoom Hybrid MMR 4.6.20211116.131_x86-64

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    7.3

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org

    3.3 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 88.4

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    99.05 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    PoC (publicly reported)
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.3
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    3.3 %
    Moderate — model estimates 1-10% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    88.4
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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.

    Source: NVD (NIST), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    Zoom Video Communications IncControllers for Zoom Rooms (for Android, iOS, and Windows)
    • < 5.8.3
    • 5.8.3
    Zoom Video Communications IncZoom Client for Meetings (for Android, iOS, Linux, macOS, and Windows)
    • < 5.8.4
    • 5.8.4
    Zoom Video Communications IncZoom Client for Meetings for Blackberry (for Android and iOS)
    • < 5.8.1
    • 5.8.1
    Zoom Video Communications IncZoom Client for Meetings for Chrome OS
    • < 5.0.1
    • 5.0.1
    Zoom Video Communications IncZoom Client for Meetings for intune (for Android and iOS)
    • < 5.8.4
    • 5.8.4
    Zoom Video Communications IncZoom Hybrid MMR
    • < 4.6.20211116.131_x86-64
    • 4.6.20211116.131_x86-64
    Zoom Video Communications IncZoom Hybrid Zproxy
    • < 1.0.1058.20211116
    • 1.0.1058.20211116
    Zoom Video Communications IncZoom Meeting SDK for Android
    • < 5.7.6.1922
    • 5.7.6.1922
    Zoom Video Communications IncZoom Meeting SDK for iOS
    • < 5.7.6.1082
    • 5.7.6.1082
    Zoom Video Communications IncZoom Meeting SDK for macOS
    • < 5.7.6.1340
    • 5.7.6.1340
    Zoom Video Communications IncZoom Meeting SDK for Windows
    • < 5.7.6.1081
    • 5.7.6.1081
    Zoom Video Communications IncZoom On-Premise Meeting Connector Controller
    • < 4.8.12.20211115
    • 4.8.12.20211115
    Zoom Video Communications IncZoom On-Premise Meeting Connector MMR
    • < 4.8.12.20211115
    • 4.8.12.20211115
    Zoom Video Communications IncZoom On-Premise Recording Connector
    • < 5.1.0.65.20211116
    • 5.1.0.65.20211116
    Zoom Video Communications IncZoom On-Premise Virtual Room Connector
    • < 4.4.7266.20211117
    • 4.4.7266.20211117
    Zoom Video Communications IncZoom On-Premise Virtual Room Connector Load Balancer
    • < 2.5.5692.20211117
    • 2.5.5692.20211117
    Zoom Video Communications IncZoom Rooms for Conference Room (for Android, AndroidBali, macOS, and Windows)
    • < 5.8.3
    • 5.8.3
    Zoom Video Communications IncZoom VDI Azure Virtual Desktop Plugins (for Windows x86 or x64, IGEL x64, Ubuntu x64, HP ThinPro OS x64)
    • < 5.8.4.21112
    • 5.8.4.21112
    Zoom Video Communications IncZoom 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)
    • < 5.8.4.21112
    • 5.8.4.21112
    Zoom Video Communications IncZoom 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)
    • < 5.8.4.21112
    • 5.8.4.21112
    Zoom Video Communications IncZoom VDI Windows Meeting Client
    • < 5.8.4
    • 5.8.4
    Zoom Video Communications IncZoom Video SDK (for Android, iOS, macOS, and Windows)
    • < 1.1.2
    • 1.1.2
    zoomandroid_meeting_sdk
    • < 5.7.6.1922
    • 5.7.6.1922
    zoomandroid_video_sdk
    • < 1.1.2
    • 1.1.2
    zoomcontrollers_for_zoom_rooms
    • < 5.8.3
    • 5.8.3
    zoomhybrid_mmr
    • < 4.6.20211116.131
    • 4.6.20211116.131
    zoomhybrid_zproxy
    • < 1.0.1058.20211116
    • 1.0.1058.20211116
    zoomiphone_os_meeting_sdk
    • < 5.7.6.1082
    • 5.7.6.1082
    zoomiphone_os_video_sdk
    • < 1.1.2
    • 1.1.2
    zoommacos_meeting_sdk
    • < 5.7.6.1340
    • 5.7.6.1340
    zoommacos_video_sdk
    • < 1.1.2
    • 1.1.2
    zoommeetings
    • < 5.8.3
    • < 5.8.4
    • 5.8.3
    • 5.8.4
    zoommeetings_for_blackberry
    • < 5.8.1
    • 5.8.1
    zoommeetings_for_chrome_os
    • < 5.0.1
    • 5.0.1
    zoommeetings_for_intune
    • < 5.8.4
    • 5.8.4
    zoomrooms_for_conference_rooms
    • < 5.8.3
    • 5.8.3
    zoomvdi_azure_virtual_desktop
    • < 5.8.4.21112
    • 5.8.4.21112
    zoomvdi_citrix
    • < 5.8.4.21112
    • 5.8.4.21112
    zoomvdi_vmware
    • < 5.8.4.21112
    • 5.8.4.21112
    zoomvdi_windows_meeting_client
    • < 5.8.4
    • 5.8.4
    zoomvirtual_desktop_infrastructure
    • < 5.8.4
    • 5.8.4
    zoomwindows_meeting_sdk
    • < 5.7.6.1081
    • 5.7.6.1081
    zoomwindows_video_sdk
    • < 1.1.2
    • 1.1.2
    zoomzoom_on-premise_meeting_connector_controller
    • < 4.8.12.20211115
    • 4.8.12.20211115
    zoomzoom_on-premise_meeting_connector_mmr
    • < 4.8.12.20211115
    • 4.8.12.20211115
    zoomzoom_on-premise_recording_connector
    • < 5.1.0.65.20211116
    • 5.1.0.65.20211116
    zoomzoom_on-premise_virtual_room_connector
    • < 4.4.7266.20211117
    • 4.4.7266.20211117

    Vendors and products

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    Packet StormZoom Chat Message Processing Buffer Overflow (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • explore.zoom.usen/trust/security/security-bulletinx_refsource_MISC, Vendor advisory
    • packetstormsecurity.comfiles/165417/Zoom-Chat-Message-Processing-Buffer-Overflow.htmlx_refsource_MISC, Third-party advisory, Vulnerability database
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    <a href="https://intel.neosec.eu/en/cve/CVE-2021-34423"><img src="https://intel.neosec.eu/badge/cve/CVE-2021-34423.svg?lang=en" alt="CVE-2021-34423 – NEOSEC Intel" height="20"></a>