CVE-2021-38651Network attack vector

Authenticated spoofing

Published Sep 15, 2021 · Updated Aug 10, 2026

Spoofing in Microsoft SharePoint servers before fixed builds allows remote authenticated users to impersonate trusted content via crafted requests. Microsoft has not disclosed the specific request-handling component or operation that causes the spoofing. The attack requires low-privilege authentication and user interaction, and the documented impact is content impersonation rather than code execution or service interruption.

CVSS severity7.6
High
EPSS probability1.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Spoofing in Microsoft SharePoint servers before fixed builds allows remote authenticated users to impersonate trusted content via crafted requests. Microsoft has not disclosed the specific request-handling component or operation that causes the spoofing. The attack requires low-privilege authentication and user interaction, and the documented impact is content impersonation rather than code execution or service interruption.

The record

CVE
CVE-2021-38651
Published
Sep 15, 2021
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Microsoft SharePoint Foundation 2013
Classifications
Unavailable
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=15.0.0 <5381.1000

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft SharePoint Foundation 2013version=15.0.0 <5381.1000
Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <5215.1000
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <10378.20002

Published CVSS scores

7.6Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
3.5NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
3.5NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

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

No sourced classifications are available.

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo