CriticalCVE-2018-8653

    Microsoft Internet Explorer Scripting Engine Memory Corruption Vulnerability (CVE-2018-8653)

    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 affects Internet Explorer 9, Internet Explorer 11, Internet Explorer 10. This CVE ID is unique from CVE-2018-8643.

    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 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 Internet Explorer 10 eq Windows Server 2012..Windows Server 2012

    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

    29.6 %

    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
    214.63 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
    29.6 %
    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

    This flaw was discovered as a zero-day in targeted attacks in 2018 and patched out-of-band by Microsoft. It is network-reachable without authentication but requires user interaction (visiting a crafted page) and higher attack complexity, which fits watering-hole and spear-phishing operations against workstations. Exploitation likelihood remains very high, while CISA does not flag known ransomware use. For organisations with current, fully patched Windows builds and IE disabled, residual risk is low. It becomes a high-priority item wherever legacy systems — Windows Server 2012, old Windows 10 builds, or line-of-business and OT/KRITIS applications tied to IE — still browse actively. Track those cases explicitly as residual risk in the NIS2 risk register.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the security update: Microsoft shipped an out-of-band update for Internet Explorer 9/10/11 in December 2018. The patch is available from the vendor — look up the per-OS KB numbers in the Microsoft advisory for CVE-2018-8653. Confirm compliance via WSUS/Intune/SCCM across every host running IE 10 (Windows Server 2012) and IE 11 (Windows 10 1507/1607/1703/1709).
      • Inventory legacy builds: Identify every Windows 10 1507–1709 and Windows Server 2012 host. These builds are out of support, and without paid extended support their patch level cannot be guaranteed. Treat them as high-risk assets and upgrade or replace them first.
      • Workaround where patching is blocked: Deny access to jscript.dll, following the workaround in Microsoft's advisory: takeown /f %windir%\system32\jscript.dll then cacls %windir%\system32\jscript.dll /E /P everyone:N. On 64-bit systems, repeat this for %windir%\syswow64\jscript.dll. Test the impact on legacy WSH/.js scripts first, and revert the workaround before patching.
      • Stop browsing from servers: Enable IE Enhanced Security Configuration on Windows Server 2012. Prohibit interactive web browsing from admin and server systems by policy.
      • Proxy quick win: Block, or at minimum separately log, outbound HTTP(S) requests with IE user agents (Trident/, MSIE) to non-allowlisted external destinations.

    2. Runbook step 2

      Mitigation layers

      • Configuration/endpoint: Disable standalone Internet Explorer via GPO ("Disable Internet Explorer 11 as a standalone browser") and redirect users to Microsoft Edge. Restrict IE mode to explicitly listed intranet sites via the Enterprise Mode Site List.
      • Endpoint hardening: Set the Internet and Restricted Sites zones to "High" and disable Active Scripting. Enable Enhanced Protected Mode. Turn on Microsoft Defender ASR rules, notably "Block JavaScript or VBScript from launching downloaded executable content".
      • Application control: Use WDAC/AppLocker or an EDR block policy to stop iexplore.exe from spawning cmd.exe, powershell.exe, wscript.exe, mshta.exe or rundll32.exe.
      • Network/IPS: Enable the CVE-2018-8653 signatures in Suricata/Snort (ET ruleset) or your NGFW IPS profile. Enforce TLS inspection for "Newly Registered Domains" and "Uncategorized" URL categories, where exploit landing pages typically live.
      • IAM/least privilege: Code runs in the logged-on user's context. Remove local admin rights, deploy LAPS, and keep privileged accounts off browsing workstations (tiering model, PAWs).

    3. Runbook step 3

      Detection rules

      • Sysmon EID 7 (image load): iexplore.exe loading the legacy jscript.dll instead of jscript9.dll. This forced legacy-engine path is typical of exploits in this class. KQL: DeviceImageLoadEvents | where InitiatingProcessFileName =~ "iexplore.exe" and FileName =~ "jscript.dll"
      • Sysmon EID 1 / Security 4688 (process creation): Suspicious child processes of the browser. Sigma shape: ParentImage|endswith: '\iexplore.exe' AND Image|endswith: ['\cmd.exe','\powershell.exe','\wscript.exe','\mshta.exe','\rundll32.exe','\regsvr32.exe'].
      • Crash telemetry: Application Event ID 1000/1001 (WER) with faulting application iexplore.exe and faulting module jscript.dll. Clusters of these crashes suggest failed exploitation attempts.
      • Proxy/Zeek telemetry: Trident/7.0 or MSIE 10.0 user agents hitting newly registered or uncategorised domains, immediately followed by executable downloads (application/octet-stream, .exe, .dll) or new outbound sessions from the same host. SPL: index=proxy http_user_agent="*Trident/*" dest_category IN ("newly_registered","uncategorized")
      • EDR behaviour: RWX memory allocations or shellcode indicators inside iexplore.exe, followed by direct external connections that bypass the proxy.

    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 affects Internet Explorer 9, Internet Explorer 11, Internet Explorer 10. This CVE ID is unique from CVE-2018-8643.

    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 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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    microsoftinternet_explorer
    • 9
    • 10
    • 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-2018-8653x_refsource_CONFIRM, Patch, Vendor advisory
    • securityfocus.com106255Vulnerability database, x_refsource_BID, Broken link, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2018-8653government-resource, US government resource
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