LiveActive security incident?Get immediate response
CVE Record

CVE-2021-34420: Zoom Windows installation executable signature bypass

The Zoom Client for Meetings for Windows installer before version 5.5.4 does not properly verify the signature of files with .msi, .ps1, and .bat extensions. This could lead to a malicious actor installing malicious software on a customer’s computer.

MediumCVSS 4.7Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-34420 affects the Zoom Client for Meetings Windows installer before 5.5.4. The installer could fail to properly verify certain file signatures, letting an attacker trick an installation flow into placing malicious software on a user’s computer.

Executive priority

Handle through standard endpoint patch governance, with priority for organizations allowing user-installed Zoom on Windows. The business risk is malicious software installation during a trusted installation process, but the provided evidence does not show KEV-listed exploitation.

Technical view

The issue is an installer signature-verification bypass for .msi, .ps1, and .bat files in Zoom Client for Meetings for Windows before 5.5.4. The CVSS vector indicates network attack vector, low complexity, no privileges, required user interaction, changed scope, and low integrity impact.

Likely exposure

Exposure is mainly Windows endpoints where users or software deployment systems used Zoom Client for Meetings installers older than 5.5.4. The bundle does not identify non-Windows Zoom products as affected.

Exploitation context

The CVE requires user interaction and targets the installer trust path, not normal meeting participation. KEV is false in the bundle, so active exploitation should be treated as unconfirmed from these sources.

Researcher notes

Evidence is limited to the CVE description, CVSS metadata, Zoom bulletin reference, and a public write-up reference. The bundle does not include detailed affected version ranges beyond before 5.5.4 or confirmed exploitation telemetry.

Mitigation direction

  • Update Zoom Client for Meetings for Windows to 5.5.4 or later.
  • Review Zoom’s security bulletin for current vendor guidance.
  • Remove old Zoom Windows installer packages from software portals and shares.
  • Use managed software deployment for Zoom installations where possible.
  • Monitor installer-related script and MSI execution on Windows endpoints.

Validation and detection

  • Inventory Windows endpoints for Zoom Client for Meetings versions before 5.5.4.
  • Check software deployment repositories for old Zoom Windows installers.
  • Review endpoint telemetry for Zoom installer activity spawning MSI, PowerShell, or batch files.
  • Confirm remediation through asset inventory or endpoint management reporting.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2021-34420 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Medium
CVSS
4.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
4.7CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N2.81.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

4.7Medium
CVSS 3.1 vector shape for CVE-2021-34420Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Zoom Video Communications IncZoom Client for Meetings for WindowsunspecifiedListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.