CVE-2023-21771Public exploit

SYSTEM privilege escalation via failed RPC impersonation

Published Jan 10, 2023 · Updated Apr 12, 2025

Elevation of privilege in Microsoft Windows Local Session Manager allows local users to gain SYSTEM privileges through an RPC race condition. LSM fails to check RpcImpersonateClient's return value, so a raced token change leaves request processing in the Local System context. A regular local account must win the timing window after LSM accepts the RPC call and before impersonation, enabling full machine control.

CVSS severity7.0
High
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Elevation of privilege in Microsoft Windows Local Session Manager allows local users to gain SYSTEM privileges through an RPC race condition. LSM fails to check RpcImpersonateClient's return value, so a raced token change leaves request processing in the Local System context. A regular local account must win the timing window after LSM accepts the RPC call and before impersonation, enabling full machine control.

The record

CVE
CVE-2023-21771
Published
Jan 10, 2023
Updated
Apr 12, 2025
Vendor
Microsoft
Product
Windows 11 version 21H2
Classifications
CWE-591, CWE-362, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 12, 2025Record 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 <10.0.22000.1455

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows 11 version 21H2version=10.0.0 <10.0.22000.1455
Microsoft · Windows 10 Version 21H2version=10.0.19043.0 <10.0.19044.2486
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.2486
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.2486
Microsoft · Windows 11, version 22H2version=10.0.22621.0 <10.0.22621.1105
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.1487

Published CVSS scores

7.0MicrosoftCVSS:3.1/AV:L/AC:H/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

CWE-591Sensitive Data Storage in Improperly Locked Memory
CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
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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