Microsoft · HTTP Protocol Stack
CVE-2021-31166
HTTP Protocol Stack Remote Code Execution Vulnerability
Exploited in attacks
Critical 9.8 Attack chance: 99.9%
What it is
HTTP Protocol Stack Remote Code Execution Vulnerability
CISA: Microsoft HTTP Protocol Stack contains a vulnerability in http.sys that allows for remote code execution.
What to do
Apply updates per vendor instructions.
Deadline for US federal agencies: April 27, 2022
More exploited flaws from Microsoft
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Oct 13, 2026 | Command Injection | Windows | High 8.8 | 9.8% |
| Sep 25, 2026 | Code Injection | SharePoint | High 8.8 | 8.2% |
| Sep 8, 2026 | Link Following | Windows | High 7.8 | 0.4% |
| Sep 8, 2026 | Heap-Based Buffer Overflow | Windows | High 7.8 | 0.4% |
| Aug 26, 2026 | Remote Code Execution | SQL Server | High 8.8 | 57% |
| Aug 18, 2026 | Double Free | Internet Key Exchange (IKE) Service Extensions | Critical 9.8 | 77% |
| Aug 18, 2026 | Weak Authentication | SharePoint | Critical 9.1 | 70% |
| Aug 11, 2026 | Windows Ancillary Function Driver for WinSock Use-After-Free | Windows Ancillary Function Driver for WinSock | High 7.0 | 0.3% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.