CVE-2021-43215Network attack vector

Unauthenticated code execution via iSNS memory corruption

Published Dec 15, 2021 · Updated Aug 4, 2024

Memory corruption in Microsoft Windows iSNS Server allows remote attackers to execute arbitrary code through crafted network requests. Microsoft has not published the packet field, parser locus, or invalid memory operation that causes the corruption. Exploitation requires network access to an enabled iSNS Server but no authentication or user interaction, and successful exploitation grants code execution in the service context.

CVSS severity9.8
Critical
EPSS probability2.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Microsoft Windows iSNS Server allows remote attackers to execute arbitrary code through crafted network requests. Microsoft has not published the packet field, parser locus, or invalid memory operation that causes the corruption. Exploitation requires network access to an enabled iSNS Server but no authentication or user interaction, and successful exploitation grants code execution in the service context.

The record

CVE
CVE-2021-43215
Published
Dec 15, 2021
Updated
Aug 4, 2024
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-787, T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=10.0.0 <10.0.10240.19145

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.0 <10.0.10240.19145
Microsoft · Windows Server 2019version=10.0.0 <10.0.17763.2366
Microsoft · Windows 7version=6.1.0 <6.1.7601.25796
Microsoft · Windows 10 Version 21H1version=10.0.0 <10.0.19043.1415
Microsoft · Windows 10 Version 1909version=10.0.0 <10.0.18363.1977
Microsoft · Windows 8.1version=6.3.0 <6.3.9600.20207
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.0 <10.0.14393.4825
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.0 <6.2.9200.23540; version=6.2.0 <6.2.9200.23545
Microsoft · Windows Server 2012version=6.2.0 <6.2.9200.23540; version=6.2.0 <6.2.9200.23545
Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19041.1415
Microsoft · Windows 10 Version 21H2version=10.0.0 <10.0.19044.1415
Microsoft · Windows Server 2016version=10.0.0 <10.0.14393.4825
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.0 <6.1.7601.25796
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.1415
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.0.0 <6.1.7601.25796
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.0 <6.3.9600.20207
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.0 <10.0.17763.2366
Microsoft · Windows 7 Service Pack 1version=6.1.0 <6.1.7601.25796
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19042.1415
Microsoft · Windows 10 Version 1607version=10.0.0 <10.0.14393.4825
Microsoft · Windows Server 2008 Service Pack 2version=6.0.0 <6.0.6003.21309
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.1415
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.2366
Microsoft · Windows Server 2012 R2version=6.3.0 <6.3.9600.20207
Microsoft · Windows Server 2008 Service Pack 2 (Server Core installation)version=6.0.0 <6.0.6003.21309

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
9.8Microsoft CorporationCVSS:3.1/AV:N/AC:L/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-787Out-of-bounds Write
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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