CVE-2021-34418Network attack vector

Unauthenticated login-service crash via unchecked NULL byte

Published Nov 11, 2021 · Updated Sep 16, 2024

Improper input validation in Zoom on-premises connector web consoles allows remote attackers to crash the login service during authentication. The login routine fails to reject a supplied NULL byte before dereferencing the resulting invalid pointer. No credentials or user interaction are required; exploitation interrupts only the affected login service, with no reported data exposure or modification.

CVSS severity5.3
Medium
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Zoom on-premises connector web consoles allows remote attackers to crash the login service during authentication. The login routine fails to reject a supplied NULL byte before dereferencing the resulting invalid pointer. No credentials or user interaction are required; exploitation interrupts only the affected login service, with no reported data exposure or modification.

The record

CVE
CVE-2021-34418
Published
Nov 11, 2021
Updated
Sep 16, 2024
Vendor
Zoom Video Communications, Inc.
Product
Zoom On-Premise Virtual Room Connector
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <4.4.6344.20200612

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zoom Video Communications, Inc. · Zoom On-Premise Virtual Room Connectorversion=unspecified <4.4.6344.20200612
Zoom Video Communications, Inc. · Zoom On-Premise Recording Connectorversion=unspecified <3.8.42.20200905
Zoom Video Communications, Inc. · Zoom On-Premise Meeting Connectorversion=unspecified <4.6.239.20200613
Zoom Video Communications, Inc. · Zoom On-Premise Virtual Room Connector Load Balancerversion=unspecified <2.5.5492.20200616
Zoom Video Communications, Inc. · Zoom On-Premise Meeting Connector MMRversion=unspecified <4.6.239.20200613

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
4.0Zoom Video Communications, Inc.CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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