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CVE-2021-31959: Scripting Engine Memory Corruption Vulnerability

• Severity: medium (CVSS 6.8 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 9.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-06-08 · updated 2026-06-17

Description

Scripting Engine Memory Corruption Vulnerability

Affected products

• Microsoft Windows 10 Version 1607: 20h2, 21h1, 1607, 1809, 1909, 2004
• Microsoft Windows 7: all versions
• Microsoft Windows 8.1: all versions
• Microsoft Windows RT 8.1: all versions
• Microsoft Windows Server 2008: r2-sp1
• Microsoft Windows Server 2012: r2
• Microsoft Windows Server 2016: all versions
• Microsoft Windows Server 2019: all versions
• Microsoft Windows 10 Version 1507: from 10.0.0 before 10.0.10240.18967 — fixed in 10.0.10240.18967
• Microsoft Windows 10 1607: from 10.0.0 before 10.0.14393.4467 — fixed in 10.0.14393.4467
• Microsoft Windows 10: from 10.0.0 before 10.0.17763.1999 — fixed in 10.0.17763.1999
• Microsoft Windows 10 1909: from 10.0.0 before 10.0.18363.1621 — fixed in 10.0.18363.1621
• Microsoft Windows 10 2004: from 10.0.0 before 10.0.19041.1052 — fixed in 10.0.19041.1052
• Microsoft Windows 10 20H2: from 10.0.0 before 10.0.19042.1052 — fixed in 10.0.19042.1052
• Microsoft Windows 10 21H1: from 10.0.0 before 10.0.19043.1052 — fixed in 10.0.19043.1052
• Microsoft Windows 7: from 6.1.0 before 6.1.7601.25632; from 6.1.0 before publication — fixed in 6.1.7601.25632, publication
• Microsoft Windows 7 Service Pack 1: from 6.1.0 before 6.1.7601.25632; from 6.1.0 before publication — fixed in 6.1.7601.25632, publication
• Microsoft Windows 8.1: from 6.3.0 before 6.3.9600.20045; from 6.3.0 before 1.0.0.0 — fixed in 6.3.9600.20045, 1.0.0.0
• Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.0 before 6.1.7601.25632; from 6.1.0 before publication — fixed in 6.1.7601.25632, publication
• Microsoft Windows Server 2012: from 6.2.0 before 6.2.9200.23372; from 6.2.0 before 1.0.0.0 — fixed in 6.2.9200.23372, 1.0.0.0
• Microsoft Windows Server 2012 R2: from 6.3.0 before 6.3.9600.20045; from 6.3.0 before 1.0.0.0 — fixed in 6.3.9600.20045, 1.0.0.0
• Microsoft Windows Server 2016: from 10.0.0 before 10.0.14393.4467 — fixed in 10.0.14393.4467
• Microsoft Windows Server 2019: from 10.0.0 before 10.0.17763.1999 — fixed in 10.0.17763.1999

How to fix

Upgrade to a fixed version: Microsoft Windows 10 Version 1507 10.0.10240.18967; Microsoft Windows 10 1607 10.0.14393.4467; Microsoft Windows 10 10.0.17763.1999; Microsoft Windows 10 1909 10.0.18363.1621; Microsoft Windows 10 2004 10.0.19041.1052; Microsoft Windows 10 20H2 10.0.19042.1052; Microsoft Windows 10 21H1 10.0.19043.1052; Microsoft Windows 7 6.1.7601.25632, publication; Microsoft Windows 7 Service Pack 1 6.1.7601.25632, publication; Microsoft Windows 8.1 6.3.9600.20045, 1.0.0.0; Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.25632, publication; Microsoft Windows Server 2012 6.2.9200.23372, 1.0.0.0. Check the vendor advisory for mitigations.

References

• http://packetstormsecurity.com/files/163056/Internet-Explorer-jscript9.dll-Memory-Corruption.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31959
• http://packetstormsecurity.com/files/163056/Internet-Explorer-jscript9.dll-Memory-Corruption.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31959

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