CVE-2021-27091Public exploit

Local SYSTEM escalation via writable service registry

Published Apr 13, 2021 · Updated Aug 3, 2024

Privilege escalation in the Microsoft Windows RPC Endpoint Mapper Service allows local users to execute code as SYSTEM. The RpcEptMapper service key grants ordinary users permission to create a Performance subkey, causing WMI performance queries to load an attacker-selected DLL. Low-privileged local access is required; Microsoft also lists Windows Server 2012 as affected, although public research does not establish whether its code path is identical.

CVSS severity7.8
High
EPSS probability0.56%
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 the Microsoft Windows RPC Endpoint Mapper Service allows local users to execute code as SYSTEM. The RpcEptMapper service key grants ordinary users permission to create a Performance subkey, causing WMI performance queries to load an attacker-selected DLL. Low-privileged local access is required; Microsoft also lists Windows Server 2012 as affected, although public research does not establish whether its code path is identical.

The record

CVE
CVE-2021-27091
Published
Apr 13, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Windows 7
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=6.1.0 <publication

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows 7version=6.1.0 <publication
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.0 <publication
Microsoft · Windows Server 2012version=6.2.0 <publication
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.0 <publication
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.0.0 <publication
Microsoft · Windows 7 Service Pack 1version=6.1.0 <publication

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

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

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Your stack

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