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CVE-2021-31166

HTTP Protocol Stack Remote Code Execution Vulnerability

CVSS 9.8 CRITICALEPSS 99.6%● KEVCWE-416
Vexday Risk Score
100Fix now
SSVC decision (CISA)
Act
Exploitation + impact → act immediately
CVSS 9.8EPSS 99.6%KEV simPoC públicaNuclei —Metasploit simPatch —
Lifecycle
11 May 2021Metasploit module available
11 May 2021Published on NVD
16 May 2021Public PoC
06 Apr 2022Active exploitation (CISA KEV)
Recommendation: Patch as soon as possible — active exploitation confirmed.
In short

A critical flaw in Windows' HTTP protocol stack allows attackers to execute arbitrary code remotely without authentication. This affects core Windows functionality used by many applications and services.

Technical detail

Use-after-free vulnerability (CWE-416) in the HTTP.sys kernel driver enables remote code execution via specially crafted HTTP requests; no authentication required, with direct kernel-level impact and system compromise.

Summary generated and translated by AI from the official description.
HTTP Protocol Stack Remote Code Execution Vulnerability
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Affected products
Microsoft · Windows 10 Version 2004Microsoft · Windows 10 Version 20H2Microsoft · Windows Server version 2004Microsoft · Windows Server version 20H2
public PoCs found — 11
githubgithub.com/0vercl0k/CVE-2021-31166★ 827githubgithub.com/ZZ-SOCMAP/CVE-2021-31166★ 19githubgithub.com/corelight/CVE-2021-31166★ 12githubgithub.com/zha0gongz1/CVE-2021-31166★ 8githubgithub.com/0xmaximus/Home-Demolisher★ 8githubgithub.com/y0g3sh-99/CVE-2021-31166-Exploit★ 7githubgithub.com/zecopro/CVE-2021-31166★ 5githubgithub.com/mvlnetdev/CVE-2021-31166-detection-rules★ 3githubgithub.com/iranzai/CVE-2021-31166-exploit★ 2githubgithub.com/bgsilvait/WIn-CVE-2021-31166★ 0cve_referencepacketstormsecurity.com/files/162722/Microsoft-HTTP-Protocol-Stack-Remote-Code-Execution.htmlunverified
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.

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References
http://packetstormsecurity.com/files/162722/Microsoft-HTTP-Protocol-Stack-Remote-Code-Execution.htmlhttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31166https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31166