CVE-2025-53771Known exploitationNetwork attack vector

Unauthenticated request spoofing via ToolPane access bypass

Published Jul 20, 2025 · Updated Feb 13, 2026

Improper authentication in Microsoft SharePoint Server allows remote attackers to spoof protected requests over a network. The ToolPane endpoint fails to restrict access to a protected API, allowing a crafted unauthenticated POST request to cross the authentication boundary. Reachability requires a network-accessible on-premises server running a build before 16.0.5513.1001 for 2016, 16.0.10417.20037 for 2019, or 16.0.18526.20508 for Subscription Edition; SharePoint Online is unaffected, and this flaw alone provides spoofed protected-API access rather than code execution.

CVSS severity6.5
Medium
EPSS probability99.73%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Microsoft SharePoint Server allows remote attackers to spoof protected requests over a network. The ToolPane endpoint fails to restrict access to a protected API, allowing a crafted unauthenticated POST request to cross the authentication boundary. Reachability requires a network-accessible on-premises server running a build before 16.0.5513.1001 for 2016, 16.0.10417.20037 for 2019, or 16.0.18526.20508 for Subscription Edition; SharePoint Online is unaffected, and this flaw alone provides spoofed protected-API access rather than code execution.

The record

CVE
CVE-2025-53771
Published
Jul 20, 2025
Updated
Feb 13, 2026
Vendor
Microsoft
Product
Microsoft SharePoint Enterprise Server 2016
Classifications
CWE-287, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 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=16.0.0 <16.0.5513.1001

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <16.0.5513.1001
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <16.0.10417.20037
Microsoft · Microsoft SharePoint Server Subscription Editionversion=16.0.0 <16.0.18526.20508

Published CVSS scores

6.5Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
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.

Reported exploitation

Technologies

Your stack

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Your stack

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