CVE-2026-55040

Think of SharePoint like your company’s filing room with a lock. This vulnerability is a flaw in the way that “lock” checks who is allowed in, letting an attacker slip past without needing a login. Once inside, they may be able to view confidential information and possibly change content.

This matters if your business runs Microsoft SharePoint Enterprise Server 2016, Microsoft SharePoint Server 2019, or Microsoft SharePoint Server Subscription Edition. The concern is higher because the issue is reachable over the network and does not require an attacker to log in. It is primarily a risk when SharePoint is exposed to attackers through network access (for example, accessible from the internet or any reachable network segment).

This is RED because a network-accessible security bypass with no authentication can directly lead to unauthorized data access and possible modification. Even though there’s no confirmed, dated exploitation in the provided reporting and no public exploit code noted, the vulnerability is considered an attractive target and new, so you should act now to close the hole.