CVE-2021-43893Public exploitNetwork attack vector

Remote privilege escalation via EFSRPC arbitrary file upload

Published Dec 15, 2021 · Updated Aug 4, 2024

Improper access control in Windows EFS allows remote authenticated users to elevate privileges through a crafted EFSRPC request. The authenticated EFSRPC service accepts a local device path encoded as a UNC path and creates attacker-supplied files or directories on the target. Exploitation requires unconstrained delegation and destination write permission; code execution requires a separate file-planting path.

CVSS severity7.5
High
EPSS probability6.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Windows EFS allows remote authenticated users to elevate privileges through a crafted EFSRPC request. The authenticated EFSRPC service accepts a local device path encoded as a UNC path and creates attacker-supplied files or directories on the target. Exploitation requires unconstrained delegation and destination write permission; code execution requires a separate file-planting path.

The record

CVE
CVE-2021-43893
Published
Dec 15, 2021
Updated
Aug 4, 2024
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-668, T1068
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 <10.0.10240.19145

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.0 <10.0.10240.19145
Microsoft · Windows Server 2019version=10.0.0 <10.0.17763.2366
Microsoft · Windows 7version=6.1.0 <6.1.7601.25796
Microsoft · Windows 10 Version 21H1version=10.0.0 <10.0.19043.1415
Microsoft · Windows 10 Version 1909version=10.0.0 <10.0.18363.1977
Microsoft · Windows 8.1version=6.3.0 <6.3.9600.20207
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.0 <10.0.14393.4825
Microsoft · Windows 11 version 21H2version=10.0.0 <10.0.22000.376
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.0 <6.2.9200.23540; version=6.2.0 <6.2.9200.23545
Microsoft · Windows Server 2012version=6.2.0 <6.2.9200.23540; version=6.2.0 <6.2.9200.23545
Microsoft · Windows Server, version 2004version=10.0.0 <10.0.19041.1415
Microsoft · Windows 10 Version 21H2version=10.0.0 <10.0.19044.1415
Microsoft · Windows Server 2016version=10.0.0 <10.0.14393.4825
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.0 <6.1.7601.25796
Microsoft · Windows 10 Version 20H2version=10.0.0 <10.0.19042.1415
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.0.0 <6.1.7601.25796
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.0 <6.3.9600.20207
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.0 <10.0.17763.2366
Microsoft · Windows 7 Service Pack 1version=6.1.0 <6.1.7601.25796
Microsoft · Windows Server version 20H2version=10.0.0 <10.0.19042.1415
Microsoft · Windows 10 Version 1607version=10.0.0 <10.0.14393.4825
Microsoft · Windows Server 2008 Service Pack 2version=6.0.0 <6.0.6003.21309
Microsoft · Windows Server 2022version=10.0.0 <10.0.20348.405
Microsoft · Windows 10 Version 2004version=10.0.0 <10.0.19041.1415
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.2366
Microsoft · Windows Server 2012 R2version=6.3.0 <6.3.9600.20207
Microsoft · Windows Server 2008 Service Pack 2 (Server Core installation)version=6.0.0 <6.0.6003.21309

Published CVSS scores

7.5Microsoft CorporationCVSS:3.1/AV:N/AC:H/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-668Exposure of Resource to Wrong Sphere
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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