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CVE Record

CVE-2021-34418: Pre-auth Null pointer crash in on-premise web console

The login routine of the web console in the Zoom On-Premise Meeting Connector before version 4.6.239.20200613, Zoom On-Premise Meeting Connector MMR before version 4.6.239.20200613, Zoom On-Premise Recording Connector before version 3.8.42.20200905, Zoom On-Premise Virtual Room Connector before version 4.4.6344.20200612, and Zoom On-Premise Virtual Room Connector Load Balancer before version 2.5.5492.20200616 fails to validate that a NULL byte was sent while authenticating. This could lead to a crash of the login service.

MediumCVSS 4Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This flaw can crash the login service for specific Zoom on-premise connector web consoles. It is an availability issue, not a data theft or account takeover issue in the provided sources. Business urgency is mainly for organizations that still operate the listed on-premise Zoom connector components below the fixed versions.

Executive priority

Treat as a targeted operational resilience issue. Prioritize remediation where on-premise Zoom connectors support business-critical meetings or recording workflows, especially if management interfaces are reachable from broad internal or external networks.

Technical view

The CVE describes missing validation of a NULL byte during authentication in the web console login routine, leading to a login service crash. Affected products are Zoom On-Premise Meeting Connector, Meeting Connector MMR, Recording Connector, Virtual Room Connector, and Virtual Room Connector Load Balancer before the specified fixed builds.

Likely exposure

Exposure appears limited to organizations running the listed Zoom on-premise connector products below the fixed versions. The source bundle does not identify Zoom’s hosted cloud service as affected. Confirm appliance inventory and exact build numbers before assuming exposure.

Exploitation context

The bundle does not cite active exploitation, and the CVE is not marked KEV. The stated impact is availability only, with no confidentiality or integrity impact. The CVSS vector lists local attack vector, while the description says pre-auth web console, so validate exposure against Zoom guidance.

Researcher notes

Evidence is limited to the CVE description, version thresholds, CVSS metadata, and Zoom bulletin reference. Do not infer broader Zoom product impact. The local CVSS vector and pre-auth web-console wording should be reconciled during vendor-guided validation.

Mitigation direction

  • Upgrade Meeting Connector and MMR to 4.6.239.20200613 or later.
  • Upgrade Recording Connector to 3.8.42.20200905 or later.
  • Upgrade Virtual Room Connector to 4.4.6344.20200612 or later.
  • Upgrade Virtual Room Connector Load Balancer to 2.5.5492.20200616 or later.
  • Review Zoom’s security bulletin for product-specific guidance and lifecycle status.

Validation and detection

  • Inventory all Zoom on-premise connector appliances and roles.
  • Record installed versions for each listed connector component.
  • Compare installed builds against the fixed versions in the CVE record.
  • Confirm the web console is not unnecessarily exposed to untrusted networks.
  • Check service logs for unexplained login service crashes.
Prepared
Confidence
medium
Sources
3

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

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CVE-2021-34418 mapping review

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

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
4 (3.1)
Known Exploited
No
Published

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

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
2Source 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
4CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L2.51.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

4Medium
CVSS 3.1 vector shape for CVE-2021-34418Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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 On-Premise Meeting ConnectorunspecifiedListed
Zoom Video Communications IncZoom On-Premise Meeting Connector MMRunspecifiedListed
Zoom Video Communications IncZoom On-Premise Recording ConnectorunspecifiedListed
Zoom Video Communications IncZoom On-Premise Virtual Room ConnectorunspecifiedListed
Zoom Video Communications IncZoom On-Premise Virtual Room Connector Load BalancerunspecifiedListed
Weakness

CWE details

No CWE listed

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