CVE-2021-31168Public exploit

Local privilege escalation via unimpersonated virtual-disk RPC

Published May 11, 2021 · Updated Aug 3, 2024

Privilege escalation in Microsoft Windows Container Manager Service allows local users to gain SYSTEM access through a virtual-disk RPC call. CmsRpcSrv_MapVirtualDiskToContainer fails to impersonate its RPC caller before HcsGrantVmAccess changes the target file DACL in the service's SYSTEM context. Low-privileged local access is sufficient; the public proof of concept demonstrates arbitrary DACL modification rather than a complete elevation chain.

CVSS severity7.8
High
EPSS probability0.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege escalation in Microsoft Windows Container Manager Service allows local users to gain SYSTEM access through a virtual-disk RPC call. CmsRpcSrv_MapVirtualDiskToContainer fails to impersonate its RPC caller before HcsGrantVmAccess changes the target file DACL in the service's SYSTEM context. Low-privileged local access is sufficient; the public proof of concept demonstrates arbitrary DACL modification rather than a complete elevation chain.

The record

CVE
CVE-2021-31168
Published
May 11, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Windows Server, version 2004
Classifications
CWE-269, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 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

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Is a vulnerable build present?

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

  1. Affected versionversion=10.0.0 <10.0.19041.982

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19041.982
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.982
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19042.982
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.982

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.8Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-269Improper Privilege Management
T1068Exploitation for Privilege Escalation

Public exploit references

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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