CVE-2021-31977Network attack vector

Unauthenticated host service interruption

Published Jun 8, 2021 · Updated Aug 3, 2024

Denial of service in Microsoft Hyper-V on affected Windows 10 and Windows Server releases allows remote attackers to interrupt the host. Microsoft has not published the faulty Hyper-V component, the accepted input, or the operation that mishandles that input. Network access without authentication or user interaction is sufficient, and successful exploitation affects availability only.

CVSS severity8.6
High
EPSS probability3.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Microsoft Hyper-V on affected Windows 10 and Windows Server releases allows remote attackers to interrupt the host. Microsoft has not published the faulty Hyper-V component, the accepted input, or the operation that mishandles that input. Network access without authentication or user interaction is sufficient, and successful exploitation affects availability only.

The record

CVE
CVE-2021-31977
Published
Jun 8, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-119, T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.0 <10.0.10240.18967

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.0 <10.0.10240.18967
Microsoft · Windows Server 2019version=10.0.0 <10.0.17763.1999
Microsoft · Windows 10 Version 21H1version=10.0.0 <10.0.19043.1052
Microsoft · Windows 10 Version 1909version=10.0.0 <10.0.18363.1621
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.0 <10.0.14393.4467
Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19041.1052
Microsoft · Windows Server 2016version=10.0.0 <10.0.14393.4467
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.0 <10.0.17763.1999
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19042.1052
Microsoft · Windows 10 Version 1607version=10.0.0 <10.0.14393.4467
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.1052
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.1999

Published CVSS scores

5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:N/A:P
8.6Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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