Microsoft MSHTML Remote Code Execution Vulnerability
A remote code execution vulnerability exists in the way that the MSHTML engine inproperly validates input, aka "MSHTML Engine Remote Code Execution Vulnerability." This affects Microsoft Office, Microsoft Office Word Viewer, Internet…
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 4 / 5
- KEV catalog (CISA)03 Nov 2021
- Exploited in EUVD (ENISA)03 Nov 2021
- Used by ransomwareno
- EPSS above 10 %53.2%
- No account, over the networkyes
What to do
Fix
Apply the vendor’s fix as soon as it is available.
CISA guidance: Apply updates per vendor instructions.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Description ENISA EUVD
A remote code execution vulnerability exists in the way that the MSHTML engine inproperly validates input, aka "MSHTML Engine Remote Code Execution Vulnerability." This affects Microsoft Office, Microsoft Office Word Viewer, Internet Explorer 9, Internet Explorer 11, Microsoft Excel Viewer, Internet Explorer 10, Office 365 ProPlus.
Affected products
- 2013 Service Pack 1 (64-bit editions)
- 365 ProPlus for 64-bit Systems
- Windows 10 Version 1803 for 32-bit Systems
- Windows 10 Version 1703 for 32-bit Systems
- Windows Server 2012 R2
- Windows 8.1 for x64-based systems
- 2016 (32-bit edition)
- Windows 10 Version 1809 for ARM64-based Systems
- Windows 10 for x64-based Systems
- Windows 7 for x64-based Systems Service Pack 1
- Windows 10 Version 1809 for x64-based Systems
- Windows 10 Version 1607 for x64-based Systems
Open source packages OSV
Affected libraries according to OSV, with fixed versions.
Timeline
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Published
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Exploitation reported (ENISA)
-
Added to the KEV catalog
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CISA remediation due date
-
EPSS peak: 53.2%
References
Other exploited vulnerabilities from the same vendor
- CVE-2026-96951Microsoft Windows Command Injection Vulnerability5.6 · Actively exploited
- CVE-2026-65660Microsoft SharePoint Code Injection Vulnerability5.0 · Actively exploited
- CVE-2026-85880Microsoft Windows Heap-Based Buffer Overflow Vulnerability4.3 · Actively exploited
- CVE-2026-81963Microsoft Windows Link Following Vulnerability4.3 · Actively exploited
- CVE-2019-1068Microsoft SQL Server Remote Code Execution Vulnerability7.0 · Actively exploited
- CVE-2026-69836Microsoft Entra5.3 · Actively exploited