Widely deployed SharePoint; RCE via deserialization; high risk.
CVE-2026-45659
Authorized deserialization in SharePoint enables remote code execution.
Is CVE-2026-45659 being exploited?
Yes. CVE-2026-45659 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-2026-45659?
CVE-2026-45659 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-2026-45659?
Yes. A fix has been recorded for CVE-2026-45659. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-45659 affect?
CVE-2026-45659 affects Microsoft Office SharePoint Server (SharePoint On-Prem & Online). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-45659?
Patch when released; implement mitigations and restrict access
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated attacker can execute code remotely via deserialization in SharePoint.
Patch when possible
- affected>= 16.0.0 and < 16.0.5552.1002
- affected>= 16.0.0 and < 16.0.10417.20128
- affected>= 16.0.0 and < 16.0.19725.20280
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.