How to fix CVE-2026-65660: Microsoft SharePoint (exploited in the wild)

Improper control of generation of code ('code injection') in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

• Severity: HIGH (CVSS 3.1 8.8, vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
• Weakness: CWE-94.
• NVD published 2026-08-11, status Analyzed.

Anyone running Microsoft SharePoint in the version ranges below. Internet-facing instances are the priority.

• microsoft sharepoint server: up to (not including) 16.0.19725.20522.

Version ranges come from the NVD CPE configuration. Confirm against the vendor advisory before you rely on them.

• Exploited in the wild: added to the CISA Known Exploited Vulnerabilities catalog on 2026-09-25; federal remediation due date 2026-09-28.

• EPSS (probability of exploitation activity in the next 30 days): 2.10%, higher than 82% of all scored CVEs (as of 2026-10-24).
• CVERadar threat level: 60/100 (see methodology).
• Likely ATT&CK techniques: T1190 Exploit Public-Facing Application (inferred); T1059 Command and Scripting Interpreter (inferred).

1. Find every instance. List where Microsoft SharePoint runs, including test, DR and forgotten internet-facing systems, and record the installed version.

   (Get-SPFarm).BuildVersion

2. Upgrade to a fixed release. microsoft sharepoint server: 16.0.19725.20522 or later. Get the build from the vendor advisory.

   # After deploying the update through Windows Update, WSUS or Intune,
   # confirm the KB from the Microsoft advisory is installed:
   Get-HotFix -Id <KB-number-from-the-advisory>

3. If you can't patch today, follow CISA's 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.
4. Verify the fix. Re-run the version check above on every instance and confirm it reports the fixed build (16.0.19725.20522 or later). Re-scan from outside if the service is exposed.
5. Hunt for signs of earlier compromise. If the system was exposed before you patched, assume it may have been hit and check the items below.
6. Rotate credentials stored on or used by the affected system if you cannot rule out compromise, and keep the logs you reviewed.

Detection hints

• T1190 Exploit Public-Facing Application: Review WAF, reverse-proxy and application logs for unusual requests to SharePoint (odd paths, oversized or encoded payloads, bursts of errors), going back to at least 2026-08-11.
• T1059 Command and Scripting Interpreter: Watch for the service process spawning shells or script interpreters.

# Process creation events (needs "Audit Process Creation" enabled)
Get-WinEvent -FilterHashtable @{ LogName = 'Security'; Id = 4688 } -MaxEvents 500 |
  Select-Object TimeCreated, Message

Detection commands are generic starting points, not CVE-specific signatures. Use the indicators from the vendor advisory when it publishes them.

• NVD: CVE-2026-65660 nvd.nist.gov/vuln/detail/CVE-2026-65660
• CVE.org record www.cve.org/CVERecord?id=CVE-2026-65660
• Microsoft Security Update Guide msrc.microsoft.com/update-guide/vulnerability/CVE-2026-65660
• CISA KEV catalog www.cisa.gov/known-exploited-vulnerabilities-catalog
• FIRST EPSS (2026-10-24) api.first.org/data/v1/epss?cve=CVE-2026-65660