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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 15 Apr 2022.
Internet ExplorerApplication · Microsoft

CVE-2018-8373

HIGH · 7.5 CVSS v3.1 Published 2018-08-15
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Remotely reachable No privileges Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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-2018-8353, CVE-2018-8355, CVE-2018-8359, CVE-2018-8371, CVE-2018-8372, CVE-2018-8385, CVE-2018-8389, CVE-2018-8390.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A remote code execution vulnerability exists in the scripting engine (JScript/VBScript) of Internet Explorer 9, 10, and 11 when handling objects in memory improperly, leading to memory corruption that could allow an attacker to execute arbitrary code via a specially crafted webpage.

MitigationApply the relevant Microsoft security update (part of August 2018 Patch Tuesday) to patch the scripting engine memory corruption. As a workaround, disable JScript/VBScript execution in Internet Explorer via Group Policy or registry, and plan migration away from Internet Explorer which is deprecated.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Internet ExplorerApplication
Affected:= 11= 10= 9

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Internet Explorer version
    Open Internet Explorer, click Help > About Internet Explorer, or run 'reg query "HKLM\SOFTWARE\Microsoft\Internet Explorer" /v Version' in Command Prompt
    Affected if The version listed is 9, 10, or 11 (any of the affected versions)
  2. Verify if August 2018 security update is installed
    Open Control Panel > Programs and Features > View installed updates, or run 'wmic qfe list | findstr "2018-08"' to list August 2018 patches
    Affected if No security update from August 2018 Patch Tuesday is installed for the scripting engine
  3. Confirm JScript/VBScript execution is enabled
    Open Internet Explorer > Internet Options > Security > Custom level, or check registry key 'HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3\1400' (3 = Internet zone)
    Affected if Script ActiveX controls marked as enabled or JScript/VBScript execution is allowed in the Internet zone
  4. Check if Internet Explorer is in active use
    Review installed programs list or check for IE shortcuts, or query 'HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\IEXPLORE.EXE'
    Affected if Internet Explorer 9, 10, or 11 is installed and potentially used

If Internet Explorer version 9, 10, or 11 is installed AND the August 2018 security update is missing AND JScript/VBScript execution is enabled, the environment is vulnerable to CVE-2018-8373.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch portal.msrc.microsoft.com →
Interim mitigation

Apply the relevant Microsoft security update (part of August 2018 Patch Tuesday) to patch the scripting engine memory corruption. As a workaround, disable JScript/VBScript execution in Internet Explorer via Group Policy or registry, and plan migration away from Internet Explorer which is deprecated.

Recommended fix High confidence

Microsoft Edge (or apply August 2018 Windows security updates for supported systems)

  1. Identify the installed Windows version and Internet Explorer version (IE 9, 10, or 11) by running 'winver' and checking the IE version via 'About Internet Explorer' in the browser.
  2. Apply Microsoft Security Update KB4343909 (August 2018 Cumulative Security Update for IE) or the equivalent monthly security update rollup for your Windows version. Download from the Microsoft Update Catalog or use Windows Update.
  3. Restart the system after applying the update.
  4. Verify the update installed successfully by checking 'View installed updates' in Control Panel and confirming KB4343909 is listed.
  5. Alternatively, if the system is end-of-life and no longer receives security updates, migrate users to Microsoft Edge or another supported browser.
Caveat Ensure compatibility with any legacy applications that require Internet Explorer features before migrating away from IE.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Internet Explorer Exploited in the wild — priority engagement
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2018-8373 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data