CVE-2021-31166
KEVMicrosoft HTTP Protocol Stack Remote Code Execution Vulnerability
Description
Microsoft HTTP Protocol Stack contains a vulnerability in http.sys that allows for remote code execution.
HTTP Protocol Stack Remote Code Execution Vulnerability
CVSS 3.1 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HPublishedMay 11, 2021
Last modifiedJun 17, 2026
Added to KEVApr 6, 2022
Remediation dueApr 27, 2022
References
- packetstormsecurity.com/files/162722/Microsoft-HTTP-Protocol-Stack-Remote-Code-Execution.htmlThird Party AdvisoryVDB Entry
- portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31166PatchVendor Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31166US Government Resource
0 recent articles mention this CVE
89
Risk assessment · Critical
Actively exploited. Patch immediately.
- Exploitation
- Confirmed in the wild (CISA KEV)
- Federal remediation deadline
- Overdue by 1643 days
- CVSS
- 9.8 CRITICAL
- EPSS (30-day exploit probability)
- 99.9% · top 1% of all CVEs
- Weakness
- CWE-416
- Attack vector
- Network, remotely reachable
- Preconditions
- No privileges and no user interaction
Recommended actions
- 1.Apply updates per vendor instructions.
- 2.Treat as emergency change: patch or isolate internet-facing instances first.
- 3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
- 4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
Assessment is derived automatically from the live signals above; verify against your own asset inventory.