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CISA KEV · ACTIVELY EXPLOITED
HIGH severity

CVE-2018-8373 — Microsoft

HIGH

CVE-2018-8373 is a high-severity (CVSS 7.5) Out-of-bounds Write vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-03-25) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

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."…

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
5 known
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-03-25. Federal agencies were required to remediate by 2022-04-15.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2018-8373.

EPSS Exploitation Probability

via FIRST.org ↗
61.5%probability of exploitation in next 30 days
High Risk-0.40%
Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk
46.0%61.0%75.9%90.9%82.5%61.5%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2018-8373 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.

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

Affected Products

1 product · 3 configurations
Application
internet explorermicrosoft
3 versions
91011
Exploits & PoCs
5

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

A remote code execution vulnerability exists in the way that the scripti…

portal.msrc.microsoft.comMSAug 2018

A remote code execution vulnerability exists in the way that the scripti…

portal.msrc.microsoft.comGoogle-sheetJul 2018

A remote code execution vulnerability exists in the way that the scripti…

blog.trendmicro.comAwesomePocJun 2020

A remote code execution vulnerability exists in the way that the scripti…

cisa.govCISAMar 2022

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    No fixed release is recorded for CVE-2018-8373 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Frequently Asked Questions

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.
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CVE-2018-8373: Microsoft Memory Corruption (KEV)