CriticalCVE-2020-0674

    Microsoft Internet Explorer Scripting Engine Memory Corruption Vulnerability (CVE-2020-0674)

    Published In CISA KEV since Sources: SingCERT, 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-2020-0673, CVE-2020-0710, CVE-2020-0711, CVE-2020-0712, CVE-2020-0713, CVE-2020-0767.

    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 10 eq Windows Server 2012..Windows Server 2012
    • 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
    • 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 9 eq Windows Server 2008 for 32-bit Systems Service Pack 2..Windows Server 2008 for 32-bit Systems Service Pack 2

    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: SingCERT, CVE.org

    86.9 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.74

    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
    217.08 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 exploitedSource: ANSSI / CERT-FR How we classify
    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
    86.9 %
    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
    99.74
    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-416

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This bug was used as a zero-day in targeted drive-by and watering-hole campaigns and remains a staple exploit-kit component. Its exploitation likelihood ranks among the highest of all CVEs. It is network-reachable without authentication and only needs a user to open a crafted page or document, although attack complexity is high. CISA does not flag known ransomware use. Typical victims are organisations running legacy line-of-business apps that depend on IE or IE mode, outdated clients and terminal servers. If IE is fully patched and disabled across your estate, residual risk is low. If you still run unsupported Windows 10 builds or Server 2012 without ESU with browsing enabled, treat this as critical and act immediately.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the February 2020 (or later) cumulative security update. The flaw sits in the legacy JScript engine jscript.dll and is fixed by the Windows/IE cumulative updates starting with the February 2020 Patch Tuesday. Look up the per-OS KB number in the Microsoft Security Update Guide for CVE-2020-0674. Verify the fix via the file version of %windir%\system32\jscript.dll and %windir%\syswow64\jscript.dll.
      • Identify unpatchable hosts now. Windows 10 1803/1809 and Windows Server 2012 without ESU no longer receive fixes. Flag them as high-risk assets, block them from internet browsing and schedule their migration.
      • Apply the Microsoft ADV200001 workaround on unpatched systems: Deny access to jscript.dll, e.g. run takeown /f %windir%\system32\jscript.dll followed by cacls %windir%\system32\jscript.dll /E /P everyone:N. Repeat for %windir%\syswow64\jscript.dll on 64-bit systems. Test side effects first (e.g. PAC/WPAD scripts, printing functions) and revert the workaround once patched.
      • Disable Internet Explorer as a browser. Block iexplore.exe or redirect to Edge via GPO/Intune. Restrict Edge IE mode to an explicit site list of internal applications.
      • Stop browsing from servers. On Windows Server hosts (especially 2012/2019 with interactive RDP users), block direct outbound HTTP/HTTPS from user sessions at the proxy.

    2. Runbook step 2

      Mitigation layers

      • Network/proxy: Restrict the IE11 user agent (Trident/7.0) to an allowlist of internal destinations. Block external destinations requested with an IE user agent, or route them through remote browser isolation.
      • IPS/web gateway: Enable signatures for JScript exploit patterns, i.e. HTML forcing the legacy engine via language="JScript.Encode" or JScript.Compact. Turn on the vendor Suricata/ET or NGFW signatures for CVE-2020-0674 and review hits before switching to block mode.
      • Endpoint hardening: Enable Defender ASR rules, notably "Block all Office applications from creating child processes" (this covers documents that render via MSHTML/IE). Enforce Exploit Protection (CFG, DEP, ASLR) for iexplore.exe and enable Enhanced Protected Mode for IE11 via GPO.
      • IAM/least privilege: Code executes as the logged-on user. Remove local admin rights and forbid browsing from admin accounts (tiering model / PAWs).
      • Configuration: Set "Active scripting" to "Disable" for the Internet zone. Where the business allows, remove IE entirely with Disable-WindowsOptionalFeature -FeatureName Internet-Explorer-Optional-amd64 -Online.

    3. Runbook step 3

      Detection rules

      • Sysmon EID 1 / EDR process ancestry: Watch for iexplore.exe (or msedge.exe in IE mode hosting MSHTML) spawning cmd.exe, powershell.exe, wscript.exe, mshta.exe, rundll32.exe or regsvr32.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "iexplore.exe" and FileName in~ ("cmd.exe","powershell.exe","wscript.exe","mshta.exe","rundll32.exe","regsvr32.exe")
      • Sysmon EID 7 (image load): Look for iexplore.exe loading jscript.dll (not jscript9.dll) while visiting external sites. This strongly indicates the legacy engine was forced. Sigma shape: selection: Image|endswith: '\iexplore.exe' and ImageLoaded|endswith: '\jscript.dll'
      • Application log, Event ID 1000/1001: iexplore.exe crashes with faulting module jscript.dll may indicate failed exploitation attempts. Centralise and correlate these events.
      • Security log, Event ID 4663: With a SACL on jscript.dll, monitor access attempts after the ADV200001 workaround is in place. Also review Event ID 4670 for unexpected ACL changes that would revert the workaround.
      • Network telemetry (Zeek/proxy): Investigate Trident/7.0 requests to newly registered or uncategorised domains, especially when the same host then immediately downloads EXE/DLL/HTA files.

    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-2020-0673, CVE-2020-0710, CVE-2020-0711, CVE-2020-0712, CVE-2020-0713, CVE-2020-0767.

    Source: CSA/SingCERT, 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 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
    • 10
    • 11
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    Vendors and products

    Weakness classes (CWE)

    • CWE-416Use After Free

      Variant

      The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

      Entry at MITRE CWE-416

    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
    ANSSI / CERT-FRLicence Ouverte 2.0, as of CERTFR-2020-ALE-006 – Vulnérabilité dans Microsoft Internet Explorer (clôturée 2020-02-19) (opens in a new tab)cert.cyber.gouv.fractively exploited
    GitHubmaxpl0it/CVE-2020-0674-Exploit (opens in a new tab)github.comPoC (publicly reported)reported, not verified—
    Packet StormMicrosoft Internet Explorer 11 Use After Free (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormMicrosoft Internet Explorer 11 Use After Free (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormMicrosoft Internet Explorer 8 11 Use After Free (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • portal.msrc.microsoft.comen-US/security-guidance/advisory/CVE-2020-0674x_refsource_MISC, Patch, Vendor advisory
    • github.commaxpl0it/CVE-2020-0674-Exploitx_refsource_MISC, Exploit, Third-party advisory
    • packetstormsecurity.comfiles/159137/Microsoft-Internet-Explorer-11-Use-After-Free.htmlx_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • packetstormsecurity.comfiles/161309/Microsoft-Internet-Explorer-11-Use-After-Free.htmlx_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • packetstormsecurity.comfiles/162565/Microsoft-Internet-Explorer-8-11-Use-After-Free.ht…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2020-0674government-resource, US government resource
    • cert.cyber.gouv.frANSSI / CERT-FR: CERTFR-2020-ALE-006 – Vulnérabilité dans Microsoft Internet Explorer (clôturée 2020-02-19)cert-fr
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