CVE-2026-65660

Published Aug 11, 2026

Last updated 25 days ago

Cloud

Server

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-65660 is a vulnerability affecting Microsoft Office SharePoint, specifically SharePoint Server 2016, 2019, and Subscription Edition, with potential impact on SharePoint 2013. This flaw stems from an improper control of code generation, characterized as a 'code injection' vulnerability. It involves a parser desynchronization issue within SharePoint's `SafeControls` filter, which is designed to prevent the loading of dangerous classes. The vulnerability arises when the `ToolPane` component processes web-part markup, failing to properly escape quotes within attribute values when reconstructing `Register` directives. This oversight allows an attacker to inject additional directives through unescaped quotes, enabling the registration of arbitrary .NET classes. While initially described by Microsoft as a spoofing vulnerability, further technical analysis revealed that CVE-2026-65660 can lead to authenticated remote code execution (RCE). Researchers have also demonstrated that this flaw can be chained with other vulnerabilities to achieve pre-authentication remote code execution on servers configured to allow anonymous page access.

Description: Improper control of generation of code ('code injection') in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Source: secure@microsoft.com
NVD status: Analyzed
Products: sharepoint_server

Risk scores

CVSS 3.1

Type: Secondary
Base score: 8.8
Impact score: 5.9
Exploitability score: 2.8
Vector string: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity: HIGH

Known exploits

Data from CISA

Vulnerability name: Microsoft SharePoint Code Injection Vulnerability
Exploit added on: Sep 25, 2026
Exploit action due: Sep 28, 2026
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.

Weaknesses

secure@microsoft.com: CWE-94

Hype score: Not currently trending

Configurations

[
  {
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:a:microsoft:sharepoint_server:*:*:*:*:subscription:*:*:*",
            "matchCriteriaId": "D918B8DF-51D1-46F3-8B3F-E4370083BEF6",
            "versionEndExcluding": "16.0.19725.20522",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:a:microsoft:sharepoint_server:2016:*:*:*:enterprise:*:*:*",
            "matchCriteriaId": "F815EF1D-7B60-47BE-9AC2-2548F99F10E4",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*",
            "matchCriteriaId": "6122D014-5BF1-4AF4-8B4D-80205ED7785E",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ]
  }
]

References

Sources include official advisories and independent security research.