---
title: "CVE-2025-53771: Microsoft SharePoint Server Spoofing Vulnerability"
url: https://erroneo.us/security/cve/CVE-2025-53771/
description: "CVE-2025-53771 (Microsoft Microsoft SharePoint Enterprise Server 2016): Improper authentication in Microsoft Office SharePoint allows an unauthorized…"
type: vulnerability-record
section: "Security Digest"
date_published: 2025-07-20
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-53771"
kev: false
cvss: 6.5
epss: 0.9989
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-53771: Microsoft SharePoint Server Spoofing Vulnerability

**Signal:** High exploit likelihood. EPSS ranks it in the top 5% of all CVEs for likely exploitation in the next 30 days. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 99.9% , percentile 100.0: FIRST’s model estimates a 99.9% chance of exploitation activity in the next 30 days, higher than 100.0% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Check exposure. ToolShell: SharePoint On-Prem Unauthenticated RCE Chain — Fixes shipped in July 2025, but ToolShell stole ASP.NET machine keys that survive patching, so any on-prem SharePoint that was internet-facing then needs proof that keys were rotated and no backdoor remains.

## What it is

Improper authentication in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.

## Affected products (CVE record)

- Microsoft Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5513.1001
- Microsoft Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20037
- Microsoft Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.18526.20508

## Severity

- microsoft CVSS 3.1: 6.5 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 99.89% probability of exploitation activity in the next 30 days; percentile 100.0.

## Sources

- [Microsoft SharePoint Server Spoofing Vulnerability](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53771)
- [CVE.org record CVE-2025-53771](https://www.cve.org/CVERecord?id=CVE-2025-53771)
- [NVD entry CVE-2025-53771](https://nvd.nist.gov/vuln/detail/CVE-2025-53771)
- [bleepingcomputer.com](https://www.bleepingcomputer.com/news/microsoft/microsoft-sharepoint-zero-day-exploited-in-rce-attacks-no-patch-available/)

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Source page: https://erroneo.us/security/cve/CVE-2025-53771/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt