CISA Warns: Act Now on SharePoint RCE Bug Under Attack

Michael Miller · 2026-07-02

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) just dropped a big warning. They added a nasty Microsoft SharePoint Server flaw to their Known Exploited Vulnerabilities (KEV) catalog. Why? Because it's being actively exploited right now. If you're running SharePoint, this is one you can't ignore. This vulnerability, officially tagged as CVE-2026-45659, carries a CVSS score of 8.8 out of 10. That's high-severity territory. It's a remote code execution (RCE) issue that stems from deserialization of untrusted data. In plain English? Attackers can send a specially crafted request to your SharePoint server and run code remotely. No user interaction needed. Just a direct path to your system. ### What Makes This Bug So Dangerous? Here's the thing about deserialization flaws: they're tricky to catch and devastating when exploited. When an application deserializes data without proper validation, it essentially trusts whatever it receives. An attacker can embed malicious code in that data stream, and boom—they're inside your network. - No authentication required to trigger the exploit - Runs with the same privileges as the SharePoint application pool - Can lead to lateral movement across your network Think of it like opening a package you didn't order. You assume it's safe, but inside could be anything. That's what happens when SharePoint deserializes untrusted data without checking what's really there. ### CISA's Directive: What You Need to Do CISA has mandated that all federal civilian executive branch agencies must patch this vulnerability by a specific deadline. While that rule applies directly to government networks, private companies should take it just as seriously. The fact that it's already being exploited means attackers are actively scanning for vulnerable servers. > "CISA added this vulnerability to the KEV catalog based on evidence of active exploitation. This is not a theoretical risk—it's happening now." ### How to Protect Your SharePoint Environment First step: check your SharePoint Server version. Microsoft has released a security update that addresses CVE-2026-45659. If you haven't applied it yet, stop everything and patch. Here's what else you should do: - Apply the official Microsoft patch immediately - Restrict network access to SharePoint servers where possible - Monitor for unusual deserialization attempts in your logs - Enable advanced threat protection if your security stack supports it Don't wait for an exploit to hit your organization. The window between disclosure and exploitation is shrinking every year. This bug is already being used in the wild, which means attackers have weaponized it. ### What About Antidetect Browsers? You might be wondering why this matters if you're in the antidetect browser space. Here's the connection: many antidetect browser users work with multiple accounts across platforms that rely on SharePoint for document management and collaboration. If your SharePoint server gets compromised, your account data could be exposed. That defeats the whole purpose of using antidetect tools for privacy. Plus, understanding how vulnerabilities like this work helps you appreciate why browser fingerprint protection matters. Attackers often use RCE bugs to deploy malware that collects fingerprint data. By protecting your browser environment, you add another layer of defense against these kinds of attacks. ### Final Thoughts CISA's KEV catalog is a clear signal. When they add a vulnerability, it means you need to act fast. CVE-2026-45659 is a serious threat, but it's also a reminder that security isn't just about one tool—it's about layering protections. Patch your systems, monitor your networks, and stay informed. If you're running SharePoint, don't assume you're safe because you haven't seen an attack. By the time you notice something wrong, it might already be too late. Patch now, ask questions later.