CVE-2026-65660: Microsoft SharePoint Code Injection Vulnerability

What it is

Microsoft SharePoint contains a code injection vulnerability which could allow an authorized attacker to execute code over a network.

What to do

Schedule the vendor fix into this week’s change window, prioritising internet-facing and business-critical systems. Confirm the fix is applied everywhere, not just where it was easy.

Priority

This week: Schedule into this week’s change window.

Severity (CVSS)

8.8 high

CISA assessment (SSVC)

actively exploited; needs manual effort per target; total control of the affected system

Exploit probability (EPSS, 30 days)

2.1%, higher than 81% of all CVEs

Added to CISA KEV

25 September 2026

CISA fix-by date

28 September 2026 (US federal agencies; a sensible deadline for everyone)

Ransomware use

Not known

Weakness

CWE-94

References

• NIST NVD entry
• CISA KEV entry
• msrc.microsoft.com/update-guide/vulnerability/CVE-2026-65660
• blog.previdian.com/cve-2026-65660-previdian-observes-two-stage-sharepoint-exploi
• www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-65660

Sources: CISA Known Exploited Vulnerabilities · FIRST Exploit Prediction Scoring System (EPSS) · NIST National Vulnerability Database · CISA Vulnrichment (SSVC), via the CVE Program. This product uses data from the NVD API but is not endorsed or certified by the NVD. Summaries are machine-written from CISA’s description; treat the vendor’s advisory as the authority for fixes.