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CVE-2026-20844: Windows Clipboard Server Privilege Elevation Vulnerability

CVE-2026-20844 · published 9 months ago

Summary

A flaw in the Windows Clipboard Server can allow an attacker to gain elevated privileges on a local system, potentially giving them control over the computer. This can happen if an attacker is able to trick the Clipboard Server into accessing memory that has already been freed, leading to unauthorized access to sensitive areas of the system. To protect against this, ensure that all Windows systems are updated with the latest security patches.

What to do

Update microsoft windows_10_1607 to version 10.0.14393.8783 or later.
Update microsoft windows_10_1809 to version 10.0.17763.8276 or later.
Update microsoft windows_10_21h2 to version 10.0.19044.6809 or later.
Update microsoft windows_10_22h2 to version 10.0.19045.6809 or later.
Update microsoft windows_11_23h2 to version 10.0.22631.6491 or later.
Update microsoft windows_11_24h2 to version 10.0.26100.7623 or later.
Update microsoft windows_11_25h2 to version 10.0.26200.7623 or later.
Update microsoft windows_server_2016 to version 10.0.14393.8783 or later.
Update microsoft windows_server_2019 to version 10.0.17763.8276 or later.
Update microsoft windows_server_2022 to version 10.0.20348.4648 or later.
Update microsoft windows_server_2022_23h2 to version 10.0.25398.2092 or later.
Update microsoft windows_server_2025 to version 10.0.26100.32230 or later.

Affected software

Vendor	Product	Affected versions
microsoft	windows_10_1607	< 10.0.14393.8783 `cpe:2.3:o:microsoft:windows_10_1607:::::::x64:*`
microsoft	windows_10_1809	< 10.0.17763.8276 `cpe:2.3:o:microsoft:windows_10_1809:::::::x64:*`
microsoft	windows_10_21h2	< 10.0.19044.6809 `cpe:2.3:o:microsoft:windows_10_21h2::::::::`
microsoft	windows_10_22h2	< 10.0.19045.6809 `cpe:2.3:o:microsoft:windows_10_22h2::::::::`
microsoft	windows_11_23h2	< 10.0.22631.6491 `cpe:2.3:o:microsoft:windows_11_23h2::::::::`
microsoft	windows_11_24h2	< 10.0.26100.7623 `cpe:2.3:o:microsoft:windows_11_24h2::::::::`
microsoft	windows_11_25h2	< 10.0.26200.7623 `cpe:2.3:o:microsoft:windows_11_25h2::::::::`
microsoft	windows_server_2016	< 10.0.14393.8783 `cpe:2.3:o:microsoft:windows_server_2016::::::::`
microsoft	windows_server_2019	< 10.0.17763.8276 `cpe:2.3:o:microsoft:windows_server_2019::::::::`
microsoft	windows_server_2022	< 10.0.20348.4648 `cpe:2.3:o:microsoft:windows_server_2022::::::::`
microsoft	windows_server_2022_23h2	< 10.0.25398.2092 `cpe:2.3:o:microsoft:windows_server_2022_23h2::::::::`
microsoft	windows_server_2025	< 10.0.26100.32230 `cpe:2.3:o:microsoft:windows_server_2025::::::::`

Original advisory text

Use after free in Windows Clipboard Server allows an unauthorized attacker to elevate privileges locally.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20844 Vendor Advisory

Fix within

Internet-facing 14 days

Internal At next upgrade

Not known to be exploited
Needs hands-on effort to exploit
Gives an attacker full control

Severity

7.4 High

Exploitation

<1% chance of attack within 30 days

Type

CWE-362Race Condition

CWE-416Use After Free

Timeline

Published13 Jan 2026

Updated4 Nov 2026

First seen7 Mar 2026

Sources

CVE-2026-20844 · NVD

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