Attackers Actively Exploiting Microsoft SharePoint Authentication Bypass (CVE-2026-55040) After Public PoC Release

Threat actors are actively exploiting CVE-2026-55040, a critical authentication bypass vulnerability in Microsoft SharePoint, following the public release of a proof-of-concept (PoC) exploit. This flaw, patched by Microsoft in July 2026, allows unauthenticated attackers to impersonate any SharePoint user or administrator by forging JWT tokens.