Rapid7 Releases PoC for SharePoint Authentication Bypass

Rapid7 published a proof-of-concept exploit for CVE-2026-55040, a critical SharePoint authentication bypass. The PoC chains four weaknesses in the JWT token validation pipeline, allowing unauthenticated attackers to forge valid tokens and impersonate site users. Rapid7's Python-based PoC can enumerate users and locate administrators, contributing to a spike in exploitation attempts.