CriticalCVE-2019-0541

    Microsoft MSHTML Remote Code Execution Vulnerability (CVE-2019-0541)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    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.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft Office eq 2010 Service Pack 2 (32-bit editions)..2010 Service Pack 2 (32-bit editions)
    • Microsoft Office eq 2010 Service Pack 2 (64-bit editions)..2010 Service Pack 2 (64-bit editions)
    • Microsoft Office eq 2013 RT Service Pack 1..2013 RT Service Pack 1
    • Microsoft Office eq 2013 Service Pack 1 (32-bit editions)..2013 Service Pack 1 (32-bit editions)
    • Microsoft Office eq 2013 Service Pack 1 (64-bit editions)..2013 Service Pack 1 (64-bit editions)
    • Microsoft Office eq 2016 (32-bit edition)..2016 (32-bit edition)
    • Microsoft Office eq 2016 (64-bit edition)..2016 (64-bit edition)
    • Microsoft Office eq 2019 for 32-bit editions..2019 for 32-bit editions
    • Microsoft Office eq 2019 for 64-bit editions..2019 for 64-bit editions
    • Microsoft Office Word Viewer eq Microsoft Office Word Viewer..Microsoft Office Word Viewer
    • Microsoft Internet Explorer 9 eq Windows Server 2008 for 32-bit Systems Service Pack 2..Windows Server 2008 for 32-bit Systems Service Pack 2
    • Microsoft Internet Explorer 9 eq Windows Server 2008 for x64-based Systems Service Pack 2..Windows Server 2008 for x64-based Systems Service Pack 2
    • Microsoft Internet Explorer 11 eq Windows 10 for 32-bit Systems..Windows 10 for 32-bit Systems
    • Microsoft Internet Explorer 11 eq Windows 10 for x64-based Systems..Windows 10 for x64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1607 for 32-bit Systems..Windows 10 Version 1607 for 32-bit Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1607 for x64-based Systems..Windows 10 Version 1607 for x64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1703 for 32-bit Systems..Windows 10 Version 1703 for 32-bit Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1703 for x64-based Systems..Windows 10 Version 1703 for x64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1709 for 32-bit Systems..Windows 10 Version 1709 for 32-bit Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1709 for ARM64-based Systems..Windows 10 Version 1709 for ARM64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1709 for x64-based Systems..Windows 10 Version 1709 for x64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1803 for 32-bit Systems..Windows 10 Version 1803 for 32-bit Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1803 for ARM64-based Systems..Windows 10 Version 1803 for ARM64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1803 for x64-based Systems..Windows 10 Version 1803 for x64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1809 for 32-bit Systems..Windows 10 Version 1809 for 32-bit Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1809 for ARM64-based Systems..Windows 10 Version 1809 for ARM64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 10 Version 1809 for x64-based Systems..Windows 10 Version 1809 for x64-based Systems
    • Microsoft Internet Explorer 11 eq Windows 7 for 32-bit Systems Service Pack 1..Windows 7 for 32-bit Systems Service Pack 1
    • Microsoft Internet Explorer 11 eq Windows 7 for x64-based Systems Service Pack 1..Windows 7 for x64-based Systems Service Pack 1
    • Microsoft Internet Explorer 11 eq Windows 8.1 for 32-bit systems..Windows 8.1 for 32-bit systems
    • Microsoft Internet Explorer 11 eq Windows 8.1 for x64-based systems..Windows 8.1 for x64-based systems
    • Microsoft Internet Explorer 11 eq Windows RT 8.1..Windows RT 8.1
    • Microsoft Internet Explorer 11 eq Windows Server 2008 R2 for x64-based Systems Service Pack 1..Windows Server 2008 R2 for x64-based Systems Service Pack 1
    • Microsoft Internet Explorer 11 eq Windows Server 2012 R2..Windows Server 2012 R2
    • Microsoft Internet Explorer 11 eq Windows Server 2016..Windows Server 2016
    • Microsoft Internet Explorer 11 eq Windows Server 2019..Windows Server 2019
    • Microsoft Excel Viewer eq 2007 Service Pack 3..2007 Service Pack 3
    • Microsoft Internet Explorer 10 eq Windows Server 2012..Windows Server 2012
    • Microsoft Office eq 365 ProPlus for 32-bit Systems..365 ProPlus for 32-bit Systems
    • Microsoft Office eq 365 ProPlus for 64-bit Systems..365 ProPlus for 64-bit Systems

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org

    53.2 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.0

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    222.38 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    53.2 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.0
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is reachable over the network without authentication. It needs only a user to open a crafted document or visit a page, and yields full code execution in the user's context, which makes it a textbook initial-access vector for phishing campaigns. Exploitation likelihood is among the highest of any CVE, though CISA does not flag known ransomware use. The organisations most exposed are those running legacy Windows 10 builds, Windows Server 2012, or IE for line-of-business apps — a common pattern in KRITIS and industrial environments. Where such hosts receive email or browse the internet, treat this as critical and remediate within 24-72 hours. On fully patched, current builds without IE, the work reduces to verifying compliance.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the updates: Push the Microsoft January 2019 security updates for Internet Explorer 9/10/11 and the affected Office components (Office, Word Viewer, Excel Viewer, Office 365 ProPlus). Look up the KB numbers per OS and Office build in the vendor advisory. Confirm installation through WSUS/Intune/SCCM compliance reporting, not just approval status.
      • Find legacy builds: Query CMDB/EDR inventory for Windows 10 1507/1607/1703/1709 and Windows Server 2012 hosts, most of which are out of support. Cut these off from web browsing and inbound email until they are updated or replaced.
      • Remove Internet Explorer: Where IE is not business-critical, remove the optional feature (Disable-WindowsOptionalFeature -Online -FeatureName Internet-Explorer-Optional-amd64) or enforce IE-to-Edge redirection via GPO. Move legacy apps into Edge IE mode with a site list.
      • Hunt retroactively: Search mail gateway and sandbox logs for Office documents (.doc, .rtf, .docx, .xls) containing embedded HTML/MHT objects or OLE links to remote URLs. Follow up on hits from the past 30 days.
      • Contain suspect endpoints: Isolate any endpoint showing suspicious child processes of WINWORD.EXE or IEXPLORE.EXE. Reset the logged-on user's credentials, since the code runs in that user's context.

    2. Runbook step 2

      Mitigation layers

      • Endpoint hardening (ASR): Enable these Defender ASR rules in block mode:
        • "Block all Office applications from creating child processes" (d4f940ab-401b-4efc-aadc-ad5f3c50688a)
        • "Block Office applications from creating executable content" (3b576869-a4ec-4529-8536-b80a7769e899)
      • Office configuration: Enforce Protected View for internet-sourced files, Outlook attachments and unsafe locations via GPO. Disable ActiveX in Office documents. Make sure archive tools propagate Mark-of-the-Web by running current 7-Zip/WinRAR versions.
      • Network/proxy: Restrict MSIE/Trident/7.0 user agents at the proxy to an allowlist of internal legacy applications. Block the "Newly Registered Domains" and "Uncategorized" categories for IE traffic.
      • Email gateway: Quarantine RTF and MHT attachments and Office files with external template or OLE references, or sanitise them with CDR (content disarm and reconstruction). Enable object and macro detonation in the sandbox.
      • Least privilege: Users run without local admin rights (LAPS, no standing admin). This keeps impact limited to the user context and makes persistence and lateral movement harder.

    3. Runbook step 3

      Detection rules

      • Process ancestry (Sysmon EID 1 / Windows 4688): Alert when ParentImage ends in \WINWORD.EXE, \EXCEL.EXE or \iexplore.exe and the child is cmd.exe, powershell.exe, mshta.exe, rundll32.exe, regsvr32.exe, wscript.exe or certutil.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("winword.exe","excel.exe","iexplore.exe") and FileName in~ ("cmd.exe","powershell.exe","mshta.exe","rundll32.exe","regsvr32.exe").
      • Module loads (Sysmon EID 7): mshtml.dll loaded into WINWORD.EXE or EXCEL.EXE, followed shortly by outbound connections (Sysmon EID 3) from the same process to external IPs.
      • File creation (Sysmon EID 11): Office or IE processes writing .exe, .dll, .hta or .ps1 files to %TEMP%, %APPDATA% or C:\Users\Public\.
      • Network telemetry (Zeek http.log / Suricata): HTTP GETs from Office user agents (Microsoft Office Word, ms-office) fetching .html/.mht resources from external domains. Also flag IE sessions to low-reputation hosts that occur just before process anomalies.
      • Defender/EDR alerts: Correlate ASR block events (Event ID 1121 in Microsoft-Windows-Windows Defender/Operational) and treat them as attempted exploitation.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    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.

    Source: cvelistv5, CISA KEV Catalog, NVD (NIST)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    MicrosoftInternet Explorer 10
    • Windows Server 2012
    • —
    MicrosoftInternet Explorer 11
    • Windows 7 for x64-based Systems Service Pack 1
    • Windows RT 8.1
    • Windows Server 2008 R2 for x64-based Systems Service Pack 1
    • Windows Server 2012 R2
    • Windows 10 Version 1809 for x64-based Systems
    • Windows Server 2016
    • Windows 10 Version 1703 for x64-based Systems
    • Windows 10 Version 1607 for 32-bit Systems
    • Windows 10 Version 1703 for 32-bit Systems
    • Windows 7 for 32-bit Systems Service Pack 1
    • Windows 8.1 for x64-based systems
    • Windows 10 Version 1809 for ARM64-based Systems
    • Windows 10 Version 1709 for 32-bit Systems
    • Windows 10 Version 1803 for x64-based Systems
    • Windows 10 for 32-bit Systems
    • Windows 10 Version 1709 for x64-based Systems
    • Windows 10 Version 1709 for ARM64-based Systems
    • Windows Server 2019
    • Windows 8.1 for 32-bit systems
    • Windows 10 Version 1809 for 32-bit Systems
    • Windows 10 Version 1803 for ARM64-based Systems
    • Windows 10 for x64-based Systems
    • Windows 10 Version 1803 for 32-bit Systems
    • Windows 10 Version 1607 for x64-based Systems
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    MicrosoftInternet Explorer 9
    • Windows Server 2008 for x64-based Systems Service Pack 2
    • Windows Server 2008 for 32-bit Systems Service Pack 2
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    MicrosoftMicrosoft Excel Viewer
    • 2007 Service Pack 3
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    MicrosoftMicrosoft Office
    • 2010 Service Pack 2 (32-bit editions)
    • 2010 Service Pack 2 (64-bit editions)
    • 2019 for 32-bit editions
    • 2013 Service Pack 1 (64-bit editions)
    • 2016 (64-bit edition)
    • 2013 Service Pack 1 (32-bit editions)
    • 2016 (32-bit edition)
    • 2019 for 64-bit editions
    • 2013 RT Service Pack 1
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    MicrosoftMicrosoft Office Word Viewer
    • Microsoft Office Word Viewer
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    MicrosoftOffice
    • 365 ProPlus for 32-bit Systems
    • 365 ProPlus for 64-bit Systems
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    microsoftexcel_viewer
    • 2007
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    microsoftinternet_explorer
    • 9
    • 10
    • 11
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    microsoftoffice
    • 2013
    • 2016
    • 2019
    • 2010
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    Vendors and products

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Exploit-DBEDB-ID 46536 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—

    References & sources

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