CVE-2021-28478Network attack vector

Authenticated content spoofing via undisclosed mechanism

Published May 11, 2021 · Updated Feb 28, 2025

Spoofing in Microsoft SharePoint Server allows remote authenticated users to alter presented content through crafted network requests. Microsoft has not published the affected component, request field, or incorrect trust decision that enables the spoofing behavior. Exploitation requires low-privilege access and victim interaction and can expose data or alter displayed content without affecting availability.

CVSS severity7.6
High
EPSS probability1.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Spoofing in Microsoft SharePoint Server allows remote authenticated users to alter presented content through crafted network requests. Microsoft has not published the affected component, request field, or incorrect trust decision that enables the spoofing behavior. Exploitation requires low-privilege access and victim interaction and can expose data or alter displayed content without affecting availability.

The record

CVE
CVE-2021-28478
Published
May 11, 2021
Updated
Feb 28, 2025
Vendor
Microsoft
Product
Microsoft SharePoint Foundation 2013
Classifications
CWE-290
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 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

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 <15.0.5345.1000

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft SharePoint Foundation 2013version=15.0.0 <15.0.5345.1000
Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <16.0.5161.1000
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <16.0.10374.20000

Published CVSS scores

7.6Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
7.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/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

CWE-290Authentication Bypass by Spoofing

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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