CVE-2021-43233Network attack vector

Remote code execution via freed RDP object

Published Dec 15, 2021 · Updated Aug 4, 2024

Use-after-free in Microsoft Windows Remote Desktop Client allows remote attackers to execute code when a user connects to a malicious RDP server. The client reuses freed memory while processing specially crafted RDP packets received from the server, enabling memory corruption and arbitrary code execution. Exploitation requires user interaction to initiate the RDP connection, and successful code runs in the client user's security context.

CVSS severity7.5
High
EPSS probability2.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Microsoft Windows Remote Desktop Client allows remote attackers to execute code when a user connects to a malicious RDP server. The client reuses freed memory while processing specially crafted RDP packets received from the server, enabling memory corruption and arbitrary code execution. Exploitation requires user interaction to initiate the RDP connection, and successful code runs in the client user's security context.

The record

CVE
CVE-2021-43233
Published
Dec 15, 2021
Updated
Aug 4, 2024
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

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 privilegesunauthenticated

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 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

Published CVSS scores

7.5Microsoft CorporationCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
5.1NIST NVDAV:N/AC:H/Au:N/C:P/I:P/A:P

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 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

T1203Exploitation for Client Execution

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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