CVE-2021-24092Public exploit

Local privilege escalation via hard-link overwrite

Published Feb 25, 2021 · Updated Aug 3, 2024

Improper privilege management in Microsoft Defender products allows local users to elevate privileges through the remediation driver. The BTR.sys kernel driver opens C:\Windows\Temp\BootClean.log with FILE_SUPERSEDE without checking whether the path is a link, allowing a crafted hard link to redirect the privileged overwrite. A low-privileged local account must arrange the link before Defender loads the transient driver during remediation; successful exploitation can overwrite arbitrary files and lead to elevated code execution.

CVSS severity7.8
High
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper privilege management in Microsoft Defender products allows local users to elevate privileges through the remediation driver. The BTR.sys kernel driver opens C:\Windows\Temp\BootClean.log with FILE_SUPERSEDE without checking whether the path is a link, allowing a crafted hard link to redirect the privileged overwrite. A low-privileged local account must arrange the link before Defender loads the transient driver during remediation; successful exploitation can overwrite arbitrary files and lead to elevated code execution.

The record

CVE
CVE-2021-24092
Published
Feb 25, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Microsoft System Center Endpoint Protection
Classifications
CWE-269, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=N/A

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft System Center Endpoint Protectionversion=N/A
Microsoft · Microsoft System Center 2012 Endpoint Protectionversion=N/A
Microsoft · Microsoft System Center 2012 R2 Endpoint Protectionversion=N/A
Microsoft · Microsoft Security Essentialsversion=N/A
Microsoft · Windows Defenderversion=N/A

Published CVSS scores

4.6NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-269Improper Privilege Management
T1068Exploitation for Privilege Escalation

Public exploit references

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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