---
title: "CVE-2026-56164: Microsoft SharePoint Server Missing Authentication for Critical Function Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-56164/
description: "CVE-2026-56164 (Microsoft SharePoint Server): Exploited in the wild (CISA KEV). Missing authentication for critical function in Microsoft Office SharePoint…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-14
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-56164"
kev: true
cvss: 5.3
epss: 0.01011
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-56164: Microsoft SharePoint Server Missing Authentication for Critical Function Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Microsoft SharePoint Server. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-07-14, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-07-17 ; treat that as the outer limit, not the target.
- EPSS 1.0% , percentile 63: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 63% of all scored CVEs (moderate). 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: Act now. SharePoint CVE-2026-56164: Exploited Unauthenticated 0-Day — Ignore the modest vendor score: this was exploited as a zero-day against on-prem SharePoint, so internet-facing farms need the July 2026 updates, a machine-key rotation and a compromise check now.

## What it is

Missing authentication for critical function in Microsoft Office SharePoint allows an unauthorized attacker to elevate privileges over a network.

## Affected products (CVE record)

- Microsoft Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001
- Microsoft Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175
- Microsoft Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434

## Severity

- microsoft CVSS 3.1: 5.3 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:F/RL:O/RC:C`

## Exploitation

- CISA KEV: added 2026-07-14; federal due date 2026-07-17. Known ransomware use: Unknown.
- CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
- CISA SSVC assessment: exploitation active , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 1.01% probability of exploitation activity in the next 30 days; percentile 63.

## Sources

- [Microsoft SharePoint Server Elevation of Privilege Vulnerability](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56164)
- [Listed in CISA KEV notes (msrc.microsoft.com)](https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-56164)
- [CVE.org record CVE-2026-56164](https://www.cve.org/CVERecord?id=CVE-2026-56164)
- [NVD entry CVE-2026-56164](https://nvd.nist.gov/vuln/detail/CVE-2026-56164)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56164)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)

---
Source page: https://erroneo.us/security/cve/CVE-2026-56164/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt