CriticalCVE-2020-0968

    Microsoft Internet Explorer Scripting Engine Memory Corruption Vulnerability (CVE-2020-0968)

    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 scripting engine handles objects in memory in Internet Explorer, aka 'Scripting Engine Memory Corruption Vulnerability'. This CVE ID is unique from CVE-2020-0970.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. 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 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 Version 1803 for 32-bit Systems..Windows 10 Version 1803 for 32-bit 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 1803 for ARM64-based Systems..Windows 10 Version 1803 for ARM64-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 x64-based Systems..Windows 10 Version 1809 for x64-based 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 Server 2019..Windows Server 2019
    • 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 x64-based Systems..Windows 10 Version 1709 for x64-based 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 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 Server 2016..Windows Server 2016
    • 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

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

    Metrics

    7.5

    Priority

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

    Source: NVD, CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org

    30.7 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 98.2

    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
    239.71 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
    7.5 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
    7.5
    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
    30.7 %
    Elevated — model estimates 10-50% exploitation likelihood.
    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
    98.2
    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
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 7 February 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-787

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is network-reachable without authentication. It does require user interaction (visiting a crafted page or opening a document) and carries higher attack complexity. The typical delivery paths are drive-by downloads via exploit kits and targeted spear-phishing. CISA flags known use in ransomware campaigns, and exploitation likelihood sits among the very highest of all scored CVEs. Treat it as high to critical wherever unpatched legacy systems remain, especially OT operator stations, line-of-business apps running in IE mode, or internet-connected terminal servers. In fully patched estates with IE disabled, verifying patch compliance is sufficient.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the security update: Roll out the Microsoft cumulative security update for Internet Explorer or the monthly Windows rollup (April 2020 Patch Tuesday or later) to every host running IE 9/10/11. The patch is available from the vendor — look up the KB number per OS version in the MSRC advisory for CVE-2020-0968. Any current cumulative update also closes the flaw.
      • Inventory patch state: Use WSUS, Intune, SCCM or Defender Vulnerability Management to find all hosts whose IE/mshtml component has not been updated since April 2020. Focus on Windows Server 2008 R2/2012, Windows 7 without ESU, embedded builds and OT HMIs.
      • Isolate unpatchable legacy assets: Cut internet access immediately for engineering workstations, HMIs and kiosks that cannot be updated. Allow outbound HTTP/HTTPS (ports 80/443) only through an allowlisting proxy.
      • Disable standalone Internet Explorer: Set the GPO "Disable Internet Explorer 11 as a standalone browser". Restrict the Enterprise Mode site list for Edge IE mode to internal URLs with a hard business need.
      • Run a compromise assessment: On hosts with stale patch levels, review 30 days of EDR telemetry for suspicious child processes of iexplore.exe (see Detection rules).

    2. Runbook step 2

      Mitigation layers

      • Endpoint hardening (script engine): Where IE must remain, restrict access to the legacy engine %windir%\system32\jscript.dll (and %windir%\syswow64\jscript.dll) via ACL, mirroring Microsoft's ADV200001 workaround: takeown /f %windir%\system32\jscript.dll, then cacls %windir%\system32\jscript.dll /E /P everyone:N. Test first, and revert the change before patching.

      • ASR rules (Defender): Enforce the following rules in block mode:

        • D3E037E1-3EB8-44C8-A917-57927947596D ("Block JavaScript or VBScript from launching downloaded executable content")
        • D4F940AB-401B-4EFC-AADC-AD5F3C50688A ("Block Office applications from creating child processes")

        The second rule covers Office documents that embed the mshtml engine.

      • Zone configuration: Use GPO to disable "Active Scripting" in the Internet and Restricted Sites zones. Enable Enhanced Protected Mode with 64-bit processes.

      • Network/proxy: At the web proxy, block the Trident/7.0 and MSIE user agents for external destinations, or allow them only for named line-of-business apps. Enable IPS signatures covering IE scripting-engine exploits (Emerging Threats EXPLOIT_KIT / WEB_CLIENT categories).

      • Privileges: Run users without local admin rights, because code executes in the logged-on user's context. Under your tiering model, privileged accounts must never browse from IE-capable workstations.

    3. Runbook step 3

      Detection rules

      • Process ancestry (Sysmon EID 1 / Security 4688): The following chain is a strong signal of successful exploitation: iexplore.exe spawning cmd.exe, powershell.exe, rundll32.exe, regsvr32.exe, mshta.exe, wscript.exe or certutil.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "iexplore.exe" and FileName in~ ("cmd.exe","powershell.exe","rundll32.exe","regsvr32.exe","mshta.exe","wscript.exe","certutil.exe")
      • Module load (Sysmon EID 7): A load of jscript.dll (not jscript9.dll) into iexplore.exe is rare and suspicious. Exploits typically force the legacy engine via language="JScript.Encode". Sigma shape: ImageLoaded|endswith: '\jscript.dll' AND Image|endswith: '\iexplore.exe'.
      • File system (Sysmon EID 11): Watch for executable content (.exe, .dll, .ps1, .hta) that iexplore.exe writes to %TEMP%, %APPDATA% or INetCache and that is executed shortly afterwards.
      • Network (Zeek/proxy): Look for IE user-agent requests to newly registered or uncategorised domains, followed within seconds by an application/octet-stream download. Correlate with Suricata ET exploit-kit landing-page rules firing on IE clients.
      • Crash telemetry (Application log EID 1000/1001): Clusters of iexplore.exe crashes with faulting module jscript.dll point to failed exploitation attempts.

    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 scripting engine handles objects in memory in Internet Explorer, aka 'Scripting Engine Memory Corruption Vulnerability'. This CVE ID is unique from CVE-2020-0970.

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

    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 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 1607 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 ARM64-based Systems
    • Windows 10 Version 1709 for x64-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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    microsoftinternet_explorer
    • 9
    • 11
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    Vendors and products

    Weakness classes (CWE)

    • CWE-787Out-of-bounds Write

      Base

      The product writes data past the end, or before the beginning, of the intended buffer.

      Entry at MITRE CWE-787

    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

    References & sources

    • portal.msrc.microsoft.comen-US/security-guidance/advisory/CVE-2020-0968x_refsource_MISC, Patch, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2020-0968government-resource, US government resource
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