---
id: CVE-2026-66808
title: Microsoft SharePoint Server Remote Code Execution Vulnerability
summary: >-
  Deserialization of untrusted data in Microsoft Office SharePoint allows an
  authorized attacker to execute code over a network.
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'
cvssSource: cna
cwe:
  - CWE-502
  - CWE-88
vendor: Microsoft
product: Microsoft SharePoint Enterprise Server 2016
affected:
  - sharepoint_enterprise_server_2016 >= 16.0.0 < 16.0.5565.1001
  - sharepoint_server_2019 >= 16.0.0 < 16.0.10417.20198
  - sharepoint_server_subscription_edition >= 16.0.0 < 16.0.19725.20522
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-08-07T00:00:00+00:00'
published: '2026-08-11'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T19:38:56.239Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-66808'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66808'
    label: Microsoft SharePoint Server Remote Code Execution Vulnerability
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-66808.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-66808'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2509774'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-66808'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-66808'
  - url: 'https://github.com/stolostron/hypershift-addon-operator/pull/766'
  - url: 'https://access.redhat.com/errata/RHSA-2026:54432'
  - url: 'https://access.redhat.com/errata/RHSA-2026:57194'
  - url: 'https://access.redhat.com/errata/RHSA-2026:59593'
  - url: 'https://access.redhat.com/errata/RHSA-2026:59579'
  - url: 'https://access.redhat.com/errata/RHSA-2026:59558'
  - url: 'https://access.redhat.com/errata/RHSA-2026:59559'
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.02044
epssPercentile: 0.80325
patched:
  - multicluster_engine_for_kubernetes 2.10
  - multicluster_engine_for_kubernetes 2.11
  - multicluster_engine_for_kubernetes 2.17
  - multicluster_engine_for_kubernetes 2.6
  - multicluster_engine_for_kubernetes 2.8
  - multicluster_engine_for_kubernetes 2.9
scores:
  cna: 8.8
  vendor: 8.7
ingestedAt: '2026-09-08T18:07:34.888Z'
---

## Overview

Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

## Affected

- `sharepoint_enterprise_server_2016 >= 16.0.0 < 16.0.5565.1001`
- `sharepoint_server_2019 >= 16.0.0 < 16.0.10417.20198`
- `sharepoint_server_subscription_edition >= 16.0.0 < 16.0.19725.20522`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:54432** · Red Hat · fixed in: multicluster engine for Kubernetes 2.10 · released 2026-08-12 · [advisory](https://access.redhat.com/errata/RHSA-2026:54432)
- **RHSA-2026:57194** · Red Hat · fixed in: multicluster engine for Kubernetes 2.11 · released 2026-08-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:57194)
- **RHSA-2026:59593** · Red Hat · fixed in: multicluster engine for Kubernetes 2.17 · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59593)
- **RHSA-2026:59579** · Red Hat · fixed in: multicluster engine for Kubernetes 2.6 · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59579)
- **RHSA-2026:59558** · Red Hat · fixed in: multicluster engine for Kubernetes 2.8 · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59558)
- **RHSA-2026:59559** · Red Hat · fixed in: multicluster engine for Kubernetes 2.9 · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59559)