CVE-2021-31166
HTTP Protocol Stack Remote Code Execution Vulnerability
- Published
- May 11, 2021
- Updated
- Oct 21, 2025
- Assigning CNA
- microsoft
- Evidence observed
- Apr 6, 2022
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HHigh · next 30 days
- Percentile
- 100.0%
- Model date
- Oct 18, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
CISA Known Exploited
This CVE appears in the CISA Known Exploited Vulnerabilities catalog.
Summary
HTTP Protocol Stack Remote Code Execution Vulnerability
Sources
modules/auxiliary/dos/windows/http/http_sys_accept_encoding_dos_cve_2021_31166.rb
Metasploit Framework modulesDeclared conditions
- platform: Windows($.auxiliary_dos/windows/http/http_sys_accept_encoding_dos_cve_2021_31166.platform)
- verification: check_not_declared($.auxiliary_dos/windows/http/http_sys_accept_encoding_dos_cve_2021_31166.check)
- CVE-2021-31166Detection
Detection rules (Suricata + Zeek) for CVE-2021-31166 HTTP Protocol Stack vulnerability, providing network-level alerts on exploit attempts against Windows IIS servers.
Responsible use
Use vulnerability information only on systems you own or are authorized to test. Kitploit links to public research metadata and does not store exploit code or malicious payloads.