CVE-2021-31166 on CISA KEV

HTTP Protocol Stack Remote Code Execution Vulnerability

01What CISA says about this vulnerability

HTTP Protocol Stack Remote Code Execution Vulnerability

02Required action — verbatim from CISA

Apply updates per vendor instructions.

03Notes & references

• portal.msrc.microsoft.com — https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-3116…
• packetstormsecurity.com — http://packetstormsecurity.com/files/162722/Microsoft-HTTP-Protocol-Stack-Remote…

04SARA's analyst layer — why this matters

This vulnerability is currently on the CISA KEV list, which CISA only adds CVEs to when there is reliable evidence of active exploitation in the wild. For federal civilian agencies, BOD 22-01 requires remediation by the due date above. For everyone else, KEV is the strongest "patch immediately" signal you can get from public threat intel.

05Affected products (summary)

Vendor	Product	Versions
Microsoft	Windows 10 Version 2004	10.0.0
Microsoft	Windows Server version 2004	10.0.0
Microsoft	Windows 10 Version 20H2	10.0.0
Microsoft	Windows Server version 20H2	10.0.0

06Detection

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection:

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