Security Digest · Vulnerability record
CVE-2025-53771: Microsoft SharePoint Server Spoofing Vulnerability
Improper authentication in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.
CVSS 6.5 Medium EPSS 99.9% · p100.0 Check exposure
Should you act?
High exploit likelihood
EPSS ranks it in the top 5% of all CVEs for likely exploitation in the next 30 days. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- 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.
Weakness type: CWE-287.
Product: Microsoft Microsoft SharePoint Enterprise Server 2016 · Assigned by: microsoft · Published: 2025-07-20
Affected and fixed versions
| Vendor | Product | Affected versions (per 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 scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoft | 3.1 | 6.5 Medium | 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 |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- 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.
Timeline
- — erroneo.us brief: ToolShell: SharePoint On-Prem Unauthenticated RCE Chain
- — CVE record published by microsoft
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Microsoft SharePoint Server Spoofing Vulnerability msrc.microsoft.com
Vulnerability records
- CVE.org record CVE-2025-53771 cve.org
- NVD entry CVE-2025-53771 nvd.nist.gov
Other references from the CVE record and advisory
- bleepingcomputer.com bleepingcomputer.com