CVE-2018-8420

A remote code execution vulnerability exists when the Microsoft XML Core Services MSXML parser processes user input, aka "MS XML Remote Code Execution Vulnerability." This affects Windows 7, Windows Server 2012 R2, Windows RT 8.1, Windows Server 2008, Windows Server 2012, Windows 8.1, Windows Server 2016, Windows Server 2008 R2, Windows 10, Windows 10 Servers.

Published: 2018-09-13 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-8420 is rated High Risk (65.5/100): CVSS High severity, with high exploitation likelihood (EPSS 48.90%, 99th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2018-8420

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 53.14% 48.90% -4.24%
2 2026-03-30 54.23% 53.14% -1.09%
3 2025-11-15 — 54.23% —

Full EPSS history (38 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-8420

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.0 HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
9.3 2.0 HIGH
AV:N/AC:M/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 8.6 10.0 [email protected]

Weakness enumeration for CVE-2018-8420

Affected software / configurations for CVE-2018-8420

Vendor Product Version Raw CPE
microsoft windows_10 — cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:*:*
microsoft windows_10 1607 cpe:2.3:o:microsoft:windows_10:1607:*:*:*:*:*:*:*
microsoft windows_10 1703 cpe:2.3:o:microsoft:windows_10:1703:*:*:*:*:*:*:*
microsoft windows_10 1709 cpe:2.3:o:microsoft:windows_10:1709:*:*:*:*:*:*:*
microsoft windows_10 1803 cpe:2.3:o:microsoft:windows_10:1803:*:*:*:*:*:*:*
microsoft windows_7 — cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:*
microsoft windows_8.1 — cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:*
microsoft windows_8.1 — cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:rt:*:*:*
microsoft windows_server 2008 cpe:2.3:o:microsoft:windows_server:2008:r2:sp1:*:*:*:itanium:*
microsoft windows_server 2008 cpe:2.3:o:microsoft:windows_server:2008:r2:sp1:*:*:*:x64:*
microsoft windows_server 2008 cpe:2.3:o:microsoft:windows_server:2008:sp2:*:*:*:*:*:*
microsoft windows_server 2012 cpe:2.3:o:microsoft:windows_server:2012:*:*:*:*:*:*:*
microsoft windows_server 2012 cpe:2.3:o:microsoft:windows_server:2012:r2:*:*:*:*:*:*
microsoft windows_server 2016 cpe:2.3:o:microsoft:windows_server:2016:*:*:*:*:*:*:*
microsoft windows_server 2016 cpe:2.3:o:microsoft:windows_server:2016:1709:*:*:*:*:*:*
microsoft windows_server 2016 cpe:2.3:o:microsoft:windows_server:2016:1803:*:*:*:*:*:*

References for CVE-2018-8420

cvelogic Threat Intelligence