CVE-2021-27070

Administrator code execution via incorrect directory permissions

Published Mar 11, 2021 · Updated Aug 19, 2026

Privilege escalation in Microsoft Windows Update Assistant before 10.0.19043.867 allows local users to execute code as Administrator. The Update Assistant assigns incorrect permissions to a directory, allowing low-privileged code to leverage that directory for arbitrary code execution. Exploitation requires existing low-privileged code execution and user interaction, and successful attacks run code in the Administrator context.

CVSS severity7.3
High
EPSS probability3.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege escalation in Microsoft Windows Update Assistant before 10.0.19043.867 allows local users to execute code as Administrator. The Update Assistant assigns incorrect permissions to a directory, allowing low-privileged code to leverage that directory for arbitrary code execution. Exploitation requires existing low-privileged code execution and user interaction, and successful attacks run code in the Administrator context.

The record

CVE
CVE-2021-27070
Published
Mar 11, 2021
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Windows Server, version 2004
Classifications
CWE-732, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 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=10.0.0 <10.0.19043.867

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19043.867
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19043.867
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19043.867
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19043.867

Published CVSS scores

7.3Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
9.3NIST NVDAV:N/AC:M/Au:N/C:C/I:C/A:C
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/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-732Incorrect Permission Assignment for Critical Resource
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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