CVE-2023-21555Network attack vector

Unauthenticated code execution via L2TP race

Published Jan 10, 2023 · Updated Jan 1, 2025

Remote code execution in Microsoft Windows L2TP allows remote attackers to execute code by sending crafted L2TP packets. Microsoft identifies a time-of-check/time-of-use race in L2TP processing but does not disclose the raced object or incorrect check/use sequence. Exploitation requires unauthenticated network access to L2TP and winning the race; success grants code execution on the target.

CVSS severity8.1
High
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in Microsoft Windows L2TP allows remote attackers to execute code by sending crafted L2TP packets. Microsoft identifies a time-of-check/time-of-use race in L2TP processing but does not disclose the raced object or incorrect check/use sequence. Exploitation requires unauthenticated network access to L2TP and winning the race; success grants code execution on the target.

The record

CVE
CVE-2023-21555
Published
Jan 10, 2023
Updated
Jan 1, 2025
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-367, T1210
Attack vector
network
Privileges
unauthenticated

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

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=10.0.10240.0 <10.0.10240.19685

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.10240.0 <10.0.10240.19685
Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.3887
Microsoft · Windows 7version=6.1.0 <6.1.7601.26321
Microsoft · Windows 8.1version=6.3.0 <6.3.9600.20778
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.5648
Microsoft · Windows 11 version 21H2version=10.0.0 <10.0.22000.1455
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.24075
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.24075
Microsoft · Windows 10 Version 21H2version=10.0.19043.0 <10.0.19044.2486
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.5648
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.7601.0 <6.1.7601.26321
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.2486
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.1.7601.0 <6.1.7601.26321
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.2486
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.20778
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.3887
Microsoft · Windows 7 Service Pack 1version=6.1.0 <6.1.7601.26321
Microsoft · Windows 11, version 22H2version=10.0.22621.0 <10.0.22621.1105
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.5648
Microsoft · Windows Server 2008 Service Pack 2version=6.0.6003.0 <6.0.6003.21872
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.1487
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.3887; version=10.0.17763.0 <10.0.17763.3887
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.20778
Microsoft · Windows Server 2008 Service Pack 2 (Server Core installation)version=6.0.6003.0 <6.0.6003.21872

Published CVSS scores

8.1MicrosoftCVSS:3.1/AV:N/AC:H/PR:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1210Exploitation of Remote Services

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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