CVE-2021-31172Network attack vector

User-assisted content spoofing

Published May 11, 2021 · Updated Feb 28, 2025

Spoofing in affected Microsoft SharePoint Server builds allows remote attackers to disclose or alter content after user interaction. Microsoft has not published the affected component, crafted input, or incorrect operation that permits the spoofing behavior. Successful exploitation requires a user to interact with attacker-controlled content and can expose sensitive data or make limited content changes without interrupting the service.

CVSS severity7.1
High
EPSS probability1.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Spoofing in affected Microsoft SharePoint Server builds allows remote attackers to disclose or alter content after user interaction. Microsoft has not published the affected component, crafted input, or incorrect operation that permits the spoofing behavior. Successful exploitation requires a user to interact with attacker-controlled content and can expose sensitive data or make limited content changes without interrupting the service.

The record

CVE
CVE-2021-31172
Published
May 11, 2021
Updated
Feb 28, 2025
Vendor
Microsoft
Product
Microsoft SharePoint Foundation 2013
Classifications
CWE-290
Attack vector
network
Privileges
unauthenticated

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

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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 <15.0.5345.1000

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

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

7.1Microsoft CorporationCVSS: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
Privilegesunauthenticated
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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