CVE-2026-55040: Microsoft SharePoint JWT Token Authentication Bypass (FIXED)

Rapid7 Labs disclosed CVE-2026-55040, a critical (CVSS 3.1 9.1) JWT token validation authentication bypass in Microsoft SharePoint that allows a remote unauthenticated attacker to perform actions as a SharePoint site user or administrator. The issue stems from flaws in the JWT validation pipeline; Rapid7 chained this with a separate RCE component (expected to be patched by Microsoft in August 2026) to achieve unauthenticated RCE in their research. The same Rapid7 feed also highlights CVE-2026-41264 (Flowise CSV Agent) — an unauthenticated RCE via crafted .csv uploads that execute arbitrary PY;