Affects Microsoft SharePoint, a widely used enterprise collaboration platform; privilege escalation in SharePoint can lead to large-scale data access and admin takeover across organizations.
CVE-2026-64921
Missing authentication in Microsoft SharePoint enables privilege escalation.
Is CVE-2026-64921 being exploited?
Not confirmed. CVE-2026-64921 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 1.00% probability of exploitation in the next 30 days.
How severe is CVE-2026-64921?
CVE-2026-64921 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-64921?
Yes. A fix has been recorded for CVE-2026-64921. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64921 affect?
CVE-2026-64921 affects Microsoft Office SharePoint, Microsoft SharePoint Server, SharePoint Online (potentially). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64921?
Apply vendor patch when released; restrict admin access, harden SharePoint networks, and monitor logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated attacker can elevate privileges over the network to site/farm admin, enabling data access, modification, and administrative control.
Immediate action required
- affected>= 16.0.0 and < 16.0.5565.1001
- affected>= 16.0.0 and < 16.0.10417.20198
- affected>= 16.0.0 and < 16.0.19725.20522
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.