Attackers Exploiting Critical SharePoint Authentication Bypass (CVE-2026-55040)

Threat actors are actively exploiting a critical authentication bypass vulnerability (CVE-2026-55040) in Microsoft SharePoint servers, allowing unauthenticated attackers to bypass authentication and perform arbitrary operations. The exploitation follows the public release of a proof-of-concept (PoC) code, with eight exploitation attempts recorded on August 12 and 13, 2026. Microsoft patched this flaw in its July 2026 Patch Tuesday updates.