Attackers Exploit SharePoint Authentication Bypass After Public PoC Release
Attackers Exploit SharePoint Authentication Bypass After Public PoC Release — Ravie LakshmananAug 13, 2026Vulnerability / Enterprise Security [https://blogg
What’s new: Attackers are exploiting a Microsoft SharePoint vulnerability (CVE-2026-55040, CVSS score: 9.1) that allows authentication bypass, following the release of a proof-of-concept (PoC) code. This vulnerability enables unauthenticated attackers to impersonate SharePoint users and perform unauthorized actions. Microsoft patched this issue in July 2026, but exploitation attempts have surged since the PoC was made public.
Who’s affected
Organizations using vulnerable versions of Microsoft SharePoint are at risk, particularly those that have not applied the July 2026 security updates.
What to do
- Ensure all SharePoint instances are updated with the latest security patches from Microsoft.
- Monitor for unusual activity or unauthorized access attempts on SharePoint servers.
- Review and enhance authentication mechanisms to mitigate risks associated with JWT token vulnerabilities.
