CVE-2020-1121

Local SYSTEM code execution via crafted application

Published May 21, 2020 · Updated Aug 19, 2026

Elevation of privilege in Microsoft Windows Clipboard Service allows local users to execute arbitrary code as Local System. Microsoft states that Windows improperly handles Clipboard Service calls but has not disclosed the responsible function or specific unsafe operation. Exploitation requires a logged-on user to run a specially crafted application, after which code executes with full Local System control over programs, data, and accounts.

CVSS severityUnavailable
Unscored
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Elevation of privilege in Microsoft Windows Clipboard Service allows local users to execute arbitrary code as Local System. Microsoft states that Windows improperly handles Clipboard Service calls but has not disclosed the responsible function or specific unsafe operation. Exploitation requires a logged-on user to run a specially crafted application, after which code executes with full Local System control over programs, data, and accounts.

The record

CVE
CVE-2020-1121
Published
May 21, 2020
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record 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=10.0.17763.0 <publication

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.17763.0 <publication
Microsoft · Windows 10 Version 1909version=10.0.0 <publication
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <publication
Microsoft · Windows Server, version 1903 (Server Core installation)version=10.0.0 <publication
Microsoft · Windows 10 Version 1809version=10.0.0 <publication; version=10.0.17763.0 <publication
Microsoft · Windows Server, version 1909 (Server Core installation)version=10.0.0 <publication
Microsoft · Windows 10 Version 1903version=10.0.0 <publication

Published CVSS scores

7.0MicrosoftCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C

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 exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

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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