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CVE-2021-31166

Microsoft HTTP Protocol Stack Remote Code Execution

9.8 CRITICALActively exploited (CISA KEV)EPSS 99.9%
  1. Published11 May 2021
  2. Added to CISA KEV6 Apr 2022
  3. Remediation due27 Apr 2022
Actively exploited (CISA KEV)

Microsoft HTTP Protocol Stack contains a vulnerability in http.sys that allows for remote code execution.

Added to KEV: 6 Apr 2022Federal remediation due: 27 Apr 2022

Description

HTTP Protocol Stack Remote Code Execution Vulnerability

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Microsoft Windows 10 2004< 10.0.19041.982
Microsoft Windows 10 20h2< 10.0.19042.982
Microsoft Windows Server 2004< 10.0.19041.982
Microsoft Windows Server 20h2< 10.0.19042.982

Remediation

Fixed in
Microsoft Windows 10 2004≥ 10.0.19041.982
Microsoft Windows 10 20h2≥ 10.0.19042.982
Microsoft Windows Server 2004≥ 10.0.19041.982
Microsoft Windows Server 20h2≥ 10.0.19042.982

References

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Frequently asked

Is CVE-2021-31166 being actively exploited?

Yes. CVE-2021-31166 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 6 Apr 2022.

How severe is CVE-2021-31166?

CVE-2021-31166 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 99.9% probability of exploitation.

Which products are affected by CVE-2021-31166?

Affected products include Microsoft Windows 10 2004, Microsoft Windows 10 20h2, Microsoft Windows Server 2004, Microsoft Windows Server 20h2.

How do I fix CVE-2021-31166?

Upgrade affected software to a fixed version, for example Microsoft Windows 10 2004 10.0.19041.982, Microsoft Windows 10 20h2 10.0.19042.982, Microsoft Windows Server 2004 10.0.19041.982 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-31166 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.