CVE-2021-34408

Local privilege escalation via junction-following log write

Published Sep 27, 2021 · Updated Aug 4, 2024

Improper link resolution in Zoom Client for Meetings for Windows before 5.3.2 allows local users to gain elevated privileges during installation. The privileged MSI installer writes logs beneath a user-writable directory and follows a junction that redirects the write into a protected location. Exploitation requires local access, a crafted junction, and an installation or update running with elevated privileges; the resulting write can enable higher-privileged command execution.

CVSS severity7.8
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper link resolution in Zoom Client for Meetings for Windows before 5.3.2 allows local users to gain elevated privileges during installation. The privileged MSI installer writes logs beneath a user-writable directory and follows a junction that redirects the write into a protected location. Exploitation requires local access, a crafted junction, and an installation or update running with elevated privileges; the resulting write can enable higher-privileged command execution.

The record

CVE
CVE-2021-34408
Published
Sep 27, 2021
Updated
Aug 4, 2024
Vendor
Zoom Video Communications, Inc.
Product
Zoom Client for Meetings for Windows
Classifications
CWE-59, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=All versions of the Zoom Client for Meetings for Windows before version 5.3.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Zoom Video Communications, Inc. · Zoom Client for Meetings for Windowsversion=All versions of the Zoom Client for Meetings for Windows before version 5.3.2

Published CVSS scores

4.6NIST National Vulnerability DatabaseAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-59Improper Link Resolution Before File Access ('Link Following')
T1068Exploitation for Privilege Escalation

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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