CVE-2021-34484Known exploitation

SYSTEM code execution via directory junction abuse

Published Aug 12, 2021 · Updated Aug 10, 2026

Privilege escalation in Microsoft Windows User Profile Service allows local users to execute arbitrary code as SYSTEM through a directory junction. The service follows an attacker-created directory junction and performs a privileged directory deletion at the redirected location. Exploitation requires low-privileged code execution on the target and yields arbitrary code execution in the SYSTEM context.

CVSS severity7.8
High
EPSS probability21.83%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege escalation in Microsoft Windows User Profile Service allows local users to execute arbitrary code as SYSTEM through a directory junction. The service follows an attacker-created directory junction and performs a privileged directory deletion at the redirected location. Exploitation requires low-privileged code execution on the target and yields arbitrary code execution in the SYSTEM context.

The record

CVE
CVE-2021-34484
Published
Aug 12, 2021
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-269, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Mar 31, 2022Exploitation reportedCISA Known Exploited Vulnerabilities Catalog listing
  3. Aug 10, 2026Record 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=10.0.10240.0 <10.0.10240.19022

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.10240.0 <10.0.10240.19022
Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.2114
Microsoft · Windows 7version=6.1.0 <6.1.7601.25685
Microsoft · Windows 10 Version 21H1version=10.0.0 <10.0.19043.1165
Microsoft · Windows 10 Version 1909version=10.0.0 <10.0.18363.1734
Microsoft · Windows 8.1version=6.3.0 <6.3.9600.20094
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.4583
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.23435
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.23435
Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19041.1165
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.4583
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.7601.0 <6.1.7601.25685
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.1165
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.1.7601.0 <6.1.7601.25685
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.20094
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.2114
Microsoft · Windows 7 Service Pack 1version=6.1.0 <6.1.7601.25685
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19042.1165
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.4583
Microsoft · Windows Server 2008 Service Pack 2version=6.0.6003.0 <6.0.6003.21192
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.1165
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.2114; version=10.0.17763.0 <10.0.17763.2114
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.20094
Microsoft · Windows Server 2008 Service Pack 2 (Server Core installation)version=6.0.6003.0 <6.0.6003.21192

Published CVSS scores

4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8Microsoft CorporationCVSS: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

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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 exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-269Improper Privilege Management
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.

Reported exploitation

Technologies

Your stack

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Your stack

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