SharePoint CVE-2026-55040: Under Active Attack

Decoy SharePoint servers are catching hackers using a new bypass. All over the world, security researchers running honeypots are watching threat actors scan for a critical vulnerability. It's the CVE-2026-55040 SharePoint bypass. If you run SharePoint in your enterprise, you need to act on this threat intelligence right now. We're seeing a massive surge in malicious activity. Threat actors are aggressively hunting for unpatched SharePoint installations. They want to exploit that CVE-2026-55040 authentication bypass to get into internal corporate networks. Since SharePoint is the crown jewel of internal data for most companies—and let's be honest, we all store way too much sensitive stuff in there—a successful hack is a worst-case scenario. Today, we're looking at what decoy servers are telling us, how to detect incoming exploit attempts, and how to verify your patches so your sysadmins and security analysts can actually get some sleep. Here are three critical pieces of threat intelligence and defense strategies you must implement today. First, check your access logs for active scanning patterns. Honeypot data shows attackers are sending specifically crafted HTTP requests to SharePoint's auth endpoints. To catch this, look for unusual HTTP requests targeting endpoints with missing or malformed auth headers. If you see repeated external probes hitting these, your organization is being scanned. Second, set up solid monitoring on decoy servers. If you use honeypots to catch hackers early, make them mimic SharePoint authentication endpoints. Threat actors use automated scripts to probe for CVE-2026-55040. If you set up simple decoys that log these bypass payloads, you can grab the attacker's IP and block them at your firewall before they ever touch your production environment. Third, run immediate patch verification. Don't just assume your updates worked. Sysadmins need to check the exact version numbers on their SharePoint instances. Compare those build numbers against Microsoft's official security advisory for CVE-2026-55040 to make sure the patch is live. Also, test the vulnerability endpoint from an unauthenticated external perspective. That's the only way to prove your web application firewall or local patch is actually blocking unauthorized access. Protecting your network starts with knowing your exposure. If you want to stay ahead of the latest CVE exploits, subscribe to the channel and hit the bell. Let me know in the comments if you've seen scanning for this bypass on your network, check the resources below for guides, and keep your shields up.