CVE-2023-21539Network attack vector

Remote code execution via undisclosed out-of-bounds read

Published Jan 10, 2023 · Updated Jan 1, 2025

Out-of-bounds read in Windows Authentication on Windows 10, Windows 11, and Server 2022 builds allows remote authenticated users to execute code. Microsoft identifies an out-of-bounds read but has not published the affected function, the input that reaches it, or the invalid read operation. Exploitation requires network access, valid low-privilege credentials, and high-complexity conditions; success grants code execution without user interaction.

CVSS severity7.5
High
EPSS probability1.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Windows Authentication on Windows 10, Windows 11, and Server 2022 builds allows remote authenticated users to execute code. Microsoft identifies an out-of-bounds read but has not published the affected function, the input that reaches it, or the invalid read operation. Exploitation requires network access, valid low-privilege credentials, and high-complexity conditions; success grants code execution without user interaction.

The record

CVE
CVE-2023-21539
Published
Jan 10, 2023
Updated
Jan 1, 2025
Vendor
Microsoft
Product
Windows 11 version 21H2
Classifications
CWE-125
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

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

What conditions does exploitation require?

Attack vectornetwork
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

7.5MicrosoftCVSS:3.1/AV:N/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read

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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