CVE-2021-40487Network attack vector

Authenticated code execution via arbitrary .NET type instantiation

Published Oct 13, 2021 · Updated Feb 28, 2025

Code injection in Microsoft SharePoint Server 2013, 2016, and 2019 allows remote authenticated users to execute arbitrary code. A crafted SetVariableActivity element causes Microsoft.SharePoint.WorkflowActions.SetVariableActivity to instantiate an arbitrary .NET type. Authentication to the workflow interface is required, and successful exploitation runs code in the web service account context.

CVSS severity8.1
High
EPSS probability48.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in Microsoft SharePoint Server 2013, 2016, and 2019 allows remote authenticated users to execute arbitrary code. A crafted SetVariableActivity element causes Microsoft.SharePoint.WorkflowActions.SetVariableActivity to instantiate an arbitrary .NET type. Authentication to the workflow interface is required, and successful exploitation runs code in the web service account context.

The record

CVE
CVE-2021-40487
Published
Oct 13, 2021
Updated
Feb 28, 2025
Vendor
Microsoft
Product
Microsoft SharePoint Foundation 2013
Classifications
CWE-94, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Feb 28, 2025Record 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=15.0.0 <15.0.5389.1000

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft SharePoint Foundation 2013version=15.0.0 <15.0.5389.1000
Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <16.0.5227.1000
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <16.0.10379.20000

Published CVSS scores

8.1Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1190Exploit Public-Facing Application

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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