Affects Microsoft Office SharePoint — widely deployed enterprise software; auth bypass at CVSS 9.1 can lead to broad data access and operational impact.
CVE-2026-55040
Auth bypass in Microsoft SharePoint enables remote unauthorized access.
Is CVE-2026-55040 being exploited?
Yes. CVE-2026-55040 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2026-55040?
CVE-2026-55040 is rated Critical with a CVSS score of 9.1. 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-2026-55040?
Yes. A fix has been recorded for CVE-2026-55040. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55040 affect?
CVE-2026-55040 affects Microsoft Office SharePoint. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55040?
Restrict SharePoint access, enable MFA, monitor logs; apply vendor patch when released.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote authentication bypass allows attackers to access SharePoint content, act as authenticated users, exfiltrate or modify site data and settings.
Immediate action required
- affected>= 16.0.0 and < 16.0.5561.1001
- affected>= 16.0.0 and < 16.0.10417.20175
- affected>= 16.0.0 and < 16.0.19725.20434
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.