ACTIVELY EXPLOITED

CVE-2021-31166: Microsoft HTTP Protocol Stack Remote Code Execution Vulnerability

Facts
VendorMicrosoft
ProductHTTP Protocol Stack
Actively exploitedYes
Added to CISA KEV6 Apr 2022
CISA federal deadline27 Apr 2022
Weakness (CWE)CWE-416

Required action (CISA's text)

Apply updates per vendor instructions.

Description (NVD)

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

SOURCES

Other Microsoft flaws

Data from NVD, CISA KEV, FIRST EPSS and vendor advisories. Updated 10 Nov 2026.