CVE-2021-33788Network attack vector

Unauthenticated service interruption via undisclosed LSA flaw

Published Jul 14, 2021 · Updated Aug 10, 2026

Denial of service in Microsoft Windows LSA allows remote attackers to interrupt affected systems through network requests. Microsoft has not disclosed the LSA code path or the operation it performs incorrectly when processing untrusted input. No authentication or user interaction is required, but published material does not state whether exploitation causes a crash, hang, or reboot.

CVSS severity7.5
High
EPSS probability3.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Microsoft Windows LSA allows remote attackers to interrupt affected systems through network requests. Microsoft has not disclosed the LSA code path or the operation it performs incorrectly when processing untrusted input. No authentication or user interaction is required, but published material does not state whether exploitation causes a crash, hang, or reboot.

The record

CVE
CVE-2021-33788
Published
Jul 14, 2021
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 10, 2026Record 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 <10.0.10240.19003

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.10240.0 <10.0.10240.19003
Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.2061
Microsoft · Windows 7version=6.1.0 <6.1.7601.25661
Microsoft · Windows 10 Version 21H1version=10.0.0 <10.0.19043.1110
Microsoft · Windows 10 Version 1909version=10.0.0 <10.0.18363.1679
Microsoft · Windows 8.1version=6.3.0 <6.3.9600.20069
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.4530
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.23409
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.23409
Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19041.1110
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.4530
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.7601.0 <6.1.7601.25661
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.1110
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.1.7601.0 <6.1.7601.25661
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.20069
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.2061
Microsoft · Windows 7 Service Pack 1version=6.1.0 <6.1.7601.25661
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19042.1110
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.4530
Microsoft · Windows Server 2008 Service Pack 2version=6.0.6003.0 <6.0.6003.21167
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.1110
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.2061; version=10.0.17763.0 <10.0.17763.2061
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.20069
Microsoft · Windows Server 2008 Service Pack 2 (Server Core installation)version=6.0.6003.0 <6.0.6003.21167

Published CVSS scores

7.5Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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.

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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

T1499Endpoint Denial of Service

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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