CVE-2021-27076Network attack vector

Authenticated code execution via InfoPath attachment deserialization

Published Mar 11, 2021 · Updated Aug 19, 2026

Deserialization in InfoPath attachment processing in Microsoft SharePoint Server allows remote authenticated users to execute arbitrary code. The attachment handler trusts tampered client-side data and deserializes it without ensuring that the serialized objects are safe. A valid SharePoint account and a crafted InfoPath attachment are required; successful exploitation runs code in the SharePoint web server process.

CVSS severity8.8
High
EPSS probability14.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization in InfoPath attachment processing in Microsoft SharePoint Server allows remote authenticated users to execute arbitrary code. The attachment handler trusts tampered client-side data and deserializes it without ensuring that the serialized objects are safe. A valid SharePoint account and a crafted InfoPath attachment are required; successful exploitation runs code in the SharePoint web server process.

The record

CVE
CVE-2021-27076
Published
Mar 11, 2021
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Microsoft SharePoint Foundation 2013
Classifications
T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 11, 2021CVE 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=15.0.0 <15.0.5327.1000

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft SharePoint Foundation 2013version=15.0.0 <15.0.5327.1000
Microsoft · Microsoft Business Productivity Servers 2010version=13.0.0.0 <14.0.7267.5000
Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <16.0.5134.1000
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <16.0.10372.20000

Published CVSS scores

6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
8.8Microsoft CorporationCVSS: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

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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