CVE-2021-43215: iSNS Server Memory Corruption Vulnerability Can Lead to Remote Code Execution

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-12-15 · updated 2026-06-17
Weakness: CWE-787

Description

iSNS Server Memory Corruption Vulnerability Can Lead to Remote Code Execution

Affected products

Microsoft Windows 10 Version 1607: 20h2, 21h1, 1607, 1809, 1909, 2004
Microsoft Windows 11 version 21H2: all versions
Microsoft Windows 7: all versions
Microsoft Windows 8.1: all versions
Microsoft Windows RT 8.1: all versions
Microsoft Windows Server: 20h2, 2022
Microsoft Windows Server 2008: r2-sp1, r2-sp2
Microsoft Windows Server 2012: r2
Microsoft Windows Server 2016: 2004
Microsoft Windows Server 2019: all versions
Microsoft Windows 10 Version 1507: from 10.0.0 before 10.0.10240.19145 — fixed in 10.0.10240.19145
Microsoft Windows 10 1607: from 10.0.0 before 10.0.14393.4825 — fixed in 10.0.14393.4825
Microsoft Windows 10: from 10.0.0 before 10.0.17763.2366 — fixed in 10.0.17763.2366
Microsoft Windows 10 1909: from 10.0.0 before 10.0.18363.1977 — fixed in 10.0.18363.1977
Microsoft Windows 10 2004: from 10.0.0 before 10.0.19041.1415 — fixed in 10.0.19041.1415
Microsoft Windows 10 20H2: from 10.0.0 before 10.0.19042.1415 — fixed in 10.0.19042.1415
Microsoft Windows 10 21H1: from 10.0.0 before 10.0.19043.1415 — fixed in 10.0.19043.1415
Microsoft Windows 10: from 10.0.0 before 10.0.19044.1415 — fixed in 10.0.19044.1415
Microsoft Windows 7: from 6.1.0 before 6.1.7601.25796 — fixed in 6.1.7601.25796
Microsoft Windows 7 Service Pack 1: from 6.1.0 before 6.1.7601.25796 — fixed in 6.1.7601.25796
Microsoft Windows 8.1: from 6.3.0 before 6.3.9600.20207 — fixed in 6.3.9600.20207
Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.0 before 6.1.7601.25796 — fixed in 6.1.7601.25796
Microsoft Windows Server 2008 Service Pack 2: from 6.0.0 before 6.0.6003.21309 — fixed in 6.0.6003.21309
Microsoft Windows Server 2012: from 6.2.0 before 6.2.9200.23545; from 6.2.0 before 6.2.9200.23540 — fixed in 6.2.9200.23545, 6.2.9200.23540
Microsoft Windows Server 2012 R2: from 6.3.0 before 6.3.9600.20207 — fixed in 6.3.9600.20207
Microsoft Windows Server 2016: from 10.0.0 before 10.0.14393.4825 — fixed in 10.0.14393.4825
Microsoft Windows Server 2019: from 10.0.0 before 10.0.17763.2366 — fixed in 10.0.17763.2366
Microsoft Windows Server version 2004: from 10.0.0 before 10.0.19041.1415 — fixed in 10.0.19041.1415
Microsoft Windows Server version 20H2: from 10.0.0 before 10.0.19042.1415 — fixed in 10.0.19042.1415

How to fix

Upgrade to a fixed version: Microsoft Windows 10 Version 1507 10.0.10240.19145; Microsoft Windows 10 1607 10.0.14393.4825; Microsoft Windows 10 10.0.17763.2366; Microsoft Windows 10 1909 10.0.18363.1977; Microsoft Windows 10 2004 10.0.19041.1415; Microsoft Windows 10 20H2 10.0.19042.1415; Microsoft Windows 10 21H1 10.0.19043.1415; Microsoft Windows 10 10.0.19044.1415; Microsoft Windows 7 6.1.7601.25796; Microsoft Windows 7 Service Pack 1 6.1.7601.25796; Microsoft Windows 8.1 6.3.9600.20207; Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.25796. Check the vendor advisory for mitigations.

References

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