Microsoft HTTP Protocol Stack Remote Code Execution Vulnerability

Added to KEV
2022-04-06
Federal due date
2022-04-27
Vendor
Microsoft
Product
HTTP Protocol Stack
EPSS
99.8th percentile (score 0.931, as of 2026-06-08)
NVD CVSS v3.1
Ransomware use
Unknown
Upstream
https://nvd.nist.gov/vuln/detail/CVE-2021-31166

CISA short description

Microsoft HTTP Protocol Stack contains a vulnerability in http.sys that allows for remote code execution.

Required action

Apply updates per vendor instructions.

EPSS percentile is the FIRST.org exploit-probability ranking as of the date noted above; it moves daily. CVSS reflects NVD's analysis at time of publication.