CVE-2021-28313Public exploit

SYSTEM privilege escalation via junction-swapped ACL update

Published Apr 13, 2021 · Updated Aug 3, 2024

Elevation of privilege in Microsoft Diagnostics Hub Standard Collector Service allows local users to gain SYSTEM access via a junction race. DiagnosticsHub.StandardCollector.Runtime.dll validates a client-selected scratch path with case-insensitive wcsnicmp, although NTFS directories can be case-sensitive. An authenticated local user with per-directory case sensitivity enabled can swap junction targets during the race, causing the SYSTEM service to rewrite a chosen file's ACL and enabling code execution as SYSTEM.

CVSS severity7.8
High
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Elevation of privilege in Microsoft Diagnostics Hub Standard Collector Service allows local users to gain SYSTEM access via a junction race. DiagnosticsHub.StandardCollector.Runtime.dll validates a client-selected scratch path with case-insensitive wcsnicmp, although NTFS directories can be case-sensitive. An authenticated local user with per-directory case sensitivity enabled can swap junction targets during the race, causing the SYSTEM service to rewrite a chosen file's ACL and enabling code execution as SYSTEM.

The record

CVE
CVE-2021-28313
Published
Apr 13, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Windows Server 2019
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 13, 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=10.0.0 <publication

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.0 <publication
Microsoft · Windows 10 Version 1909version=10.0.0 <publication
Microsoft · Windows 10 Version 1803version=10.0.0 <publication
Microsoft · Microsoft Visual Studio 2019 version 16.7version=16.0.0 <publication
Microsoft · Microsoft Visual Studio 2015version=14.0.0 <publication
Microsoft · Windows Server, version 2004version=10.0.0 <publication
Microsoft · Windows 10 Version 20H2version=10.0.0 <publication
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.0 <publication
Microsoft · Microsoft Visual Studio 2019 version 16.4version=16.0 <publication
Microsoft · Windows Server version 20H2version=10.0.0 <publication
Microsoft · Microsoft Visual Studio 2017version=15.9.0 <publication
Microsoft · Windows 10 Version 2004version=10.0.0 <publication
Microsoft · Microsoft Visual Studio 2019 version 16.9version=15.0.0 <publication
Microsoft · Windows 10 Version 1809version=10.0.0 <publication
Microsoft · Windows Server, version 1909 (Server Core installation)version=10.0.0 <publication

Published CVSS scores

7.8MicrosoftCVSS: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 exploitPublished

Weakness, pattern, technique

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo