Critical

Buffer Overflow in Zoom Client and SDKs (CVE-2021-34423)

IdentifiersCVE-2021-34423CWE-120· Buffer Copy without Checking Size…

A buffer overflow vulnerability exists in multiple Zoom products, including Zoom Client for Meetings, Zoom Rooms, Zoom VDI plugins, Zoom Meeting SDK, Zoom Video SDK, and various on-premise Zoom components, across all major platforms (Android, iOS, Linux, macOS, Windows, Chrome OS, and thin client OSes). The vulnerability is present in versions prior to the specified fixed releases (generally 5.8.4 or earlier, with some components having different version thresholds). The flaw allows an attacker to trigger a buffer overflow, which can result in a crash (denial of service) or potentially arbitrary code execution within the context of the affected application.

For your environment

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation of this vulnerability can allow a remote or local attacker to crash the Zoom application or service, leading to a denial of service. More critically, the attacker may be able to execute arbitrary code with the privileges of the user running the Zoom software, potentially leading to full compromise of the affected system.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, restrict access to vulnerable Zoom services and limit exposure by using network segmentation and access controls. Monitor for abnormal application crashes or suspicious activity related to Zoom processes. Consider disabling or uninstalling unused Zoom components until patches can be applied.

Remediation

Patch, then assume compromise.

Upgrade all affected Zoom products to the versions specified as fixed: Zoom Client for Meetings 5.8.4 or later, Zoom Rooms 5.8.3 or later, Zoom VDI plugins 5.8.4.21112 or later, Zoom Meeting SDK 5.7.6.x or later, Zoom Video SDK 1.1.2 or later, and all other listed components to their respective fixed versions. Refer to Zoom's official security advisory for the full list of affected products and fixed versions.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Zoom CommunicationsAndroid Meeting Sdkapplication

Zoom CommunicationsAndroid Video Sdkapplication

Zoom CommunicationsControllers For Zoom Roomsapplication

Zoom CommunicationsHybrid Mmrapplication

Zoom CommunicationsHybrid Zproxyapplication

Zoom CommunicationsIphone Os Meeting Sdkapplication

Zoom CommunicationsIphone Os Video Sdkapplication

Zoom CommunicationsMacos Meeting Sdkapplication

Zoom CommunicationsMacos Video Sdkapplication

Zoom CommunicationsMeetingsapplication

Zoom CommunicationsMeetings For Blackberryapplication

Zoom CommunicationsMeetings For Chrome Osapplication

Zoom CommunicationsMeetings For Intuneapplication

Zoom CommunicationsRooms For Conference Roomsapplication

Zoom CommunicationsVdi Azure Virtual Desktopapplication

Zoom CommunicationsVdi Citrixapplication

Zoom CommunicationsVdi Vmwareapplication

Zoom CommunicationsVdi Windows Meeting Clientapplication

Zoom CommunicationsVirtual Desktop Infrastructureapplication

Zoom CommunicationsWindows Meeting Sdkapplication

Zoom CommunicationsWindows Video Sdkapplication

Zoom CommunicationsZoom On-Premise Meeting Connector Controllerapplication

Zoom CommunicationsZoom On-Premise Meeting Connector Mmrapplication

Zoom CommunicationsZoom On-Premise Recording Connectorapplication

Zoom CommunicationsZoom On-Premise Virtual Room Connectorapplication

Zoom CommunicationsZoom On-Premise Virtual Room Connector Load Balancerapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

1 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

1 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity1

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2021-34423

NVD

nvd.nist.gov/vuln/detail/CVE-2021-34423

MITRE CWE · CWE-120

Buffer Copy without Checking Size of Input…

Vendor Advisory

explore.zoom.us/en/trust/security/security-bulletin

Third Party Advisory

packetstormsecurity.com/files/165417/Zoom-Chat-Message-Processing-Buffer-Overflow.html