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Microsoft SharePoint Server Remote Code Execution Vulnerability

IdentifiersCVE-2026-40365CWE-1220· Insufficient Granularity of Access…

CVE-2026-40365 is a critical remote code execution vulnerability in Microsoft SharePoint Server caused by insufficient granularity of access control. The flaw allows an authenticated attacker to send crafted network requests to a vulnerable SharePoint server and execute arbitrary code on the server. Multiple supporting sources describe the issue as an access-control weakness in SharePoint Server, and several specifically note that exploitation is possible for an authenticated user with at least Site Owner privileges. Microsoft’s advisory summary further states that successful exploitation allows the attacker to write arbitrary code and achieve remote code execution on the SharePoint Server.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation results in remote code execution on the SharePoint Server in the security context available to the vulnerable service/application. This can provide a strong foothold inside the target environment, enabling follow-on activity such as deeper network traversal, theft of organizational data, and compromise of additional systems. The impact is high across confidentiality, integrity, and availability because an attacker can run arbitrary code on a central collaboration platform that often has access to sensitive content and enterprise integrations.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure by limiting SharePoint access to trusted users and networks, minimizing the number of accounts with Site Owner or equivalent elevated SharePoint privileges, and closely monitoring SharePoint servers for suspicious authenticated activity and unexpected code execution behavior. Because this is a post-authentication server-side RCE, restricting administrative and high-privilege SharePoint roles and reducing network reachability can lower risk, but patching is the primary mitigation.

Remediation

Patch, then assume compromise.

Apply the official Microsoft security update for all affected SharePoint Server installations as part of the May 2026 Patch Tuesday release. The provided advisory states that the same KB update applies to both SharePoint Server 2016 and SharePoint Enterprise Server 2016. Given SharePoint’s exposure and history as a target for post-authentication exploit chains, on-premises farms should be updated without delay.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Microsoft CorporationSharepoint Enterprise Serverapplication
Microsoft CorporationSharepoint Serverapplication
Microsoft CorporationSharepoint Server 2016application
Microsoft CorporationSharepoint Server 2019application

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity2

Community discussion across Reddit, Mastodon, and other social sources.