Microsoft SharePoint is widely deployed; a networked privilege-escalation via signature verification bypass can impact many enterprises and warrants broad IT/infosec attention.
CVE-2026-102866
Crypto-signature bypass in SharePoint enabling privilege escalation
Is CVE-2026-102866 being exploited?
Not confirmed. CVE-2026-102866 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 0.55% probability of exploitation in the next 30 days.
How severe is CVE-2026-102866?
CVE-2026-102866 is rated High with a CVSS score of 8.1. 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-2026-102866?
Yes. A fix has been recorded for CVE-2026-102866. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-102866 affect?
CVE-2026-102866 affects Microsoft SharePoint (supported versions), Windows servers hosting SharePoint. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-102866?
Apply Microsoft update immediately; limit SharePoint network exposure and monitor logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypasses cryptographic signature checks in SharePoint, enabling remote privilege escalation to elevated SharePoint/Windows accounts and potential lateral movement.
Immediate action required
- affected>= 16.0.0 and < 16.0.20326.20190
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.