Critical CVSS 8.4 EPSS 0.09043 2020-04 archive

Executive Summary

A remote code execution vulnerability exists when Windows Hyper-V on a host server fails to properly validate input from an authenticated user on a guest operating system. To exploit the vulnerability, an attacker could run a specially crafted application on a guest operating system that could cause the Hyper-V host operating system to execute arbitrary code. An attacker who successfully exploited the vulnerability could execute arbitrary code on the host operating system. The security update addresses the vulnerability by correcting how Hyper-V validates guest operating system user input.

Overview

8.4
CVSS HIGH
Critical
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
Category Remote Code Execution
Released Apr 14 2020
Last Updated Apr 14 2020
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.09043 — 0.94619 percentile
NVD CVSS 8.4 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C
ATTACK VECTOR
Adjacent_network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
High
USER INTERACTION
None
SCOPE
Changed
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Proof-of-Concept
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 7.6

EPSS Score

0.09043
probability of exploitation in the next 30 days
0.94619 percentile - updated 2026-06-21
View on FIRST.org

Affected Products

7 affected products
Product KB Article Severity Impact Restart Required
Windows 10 Version 1809 for x64-based Systems 4549949 (Security Update) Critical Remote Code Execution Yes
Windows 10 Version 1903 for x64-based Systems 4549951 (Security Update) Critical Remote Code Execution Yes
Windows 10 Version 1909 for x64-based Systems 4549951 (Security Update) Critical Remote Code Execution Yes
Windows Server 2019 4549949 (Security Update) Critical Remote Code Execution Yes
Windows Server 2019 (Server Core installation) 4549949 (Security Update) Critical Remote Code Execution Yes
Windows Server, version 1903 (Server Core installation) 4549951 (Security Update) Critical Remote Code Execution Yes
Windows Server, version 1909 (Server Core installation) 4549951 (Security Update) Critical Remote Code Execution Yes

Patches

2 patches
Article Type Restart
4549949 Security Update Yes
4549951 Security Update Yes

Known Exploits

Acknowledgments

Microsoft Virtualization Security Team