CVE-2025-53770: 
vulnerability analysis and mitigation

CVE-2025-53770 is a critical vulnerability in on-premises Microsoft SharePoint Server that allows an unauthorized attacker to execute code over a network. Discovered in July 2025, this vulnerability affects SharePoint Server Subscription Edition, SharePoint 2019, and SharePoint 2016, while SharePoint Online in Microsoft 365 is not impacted. The vulnerability carries a CVSS score of 9.8 (Critical) and has been actively exploited in the wild (MSRC Blog, NVD).

The vulnerability involves a deserialization of untrusted data issue that allows attackers to bypass authentication controls. It is related to the way SharePoint handles ViewState objects and machine key validation. Attackers can exploit this by targeting the /layouts/15/ToolPane.aspx endpoint with specific HTTP headers, leading to remote code execution. The exploit chain involves extracting SharePoint server's MachineKey configuration and ValidationKey, which can then be used to craft malicious _VIEWSTATE payloads (Eye Security, Ars Technica).

The vulnerability enables attackers to gain complete control of affected SharePoint servers without authentication, bypassing identity protections such as MFA and SSO. Once compromised, attackers can access all SharePoint content, system files, and configurations, potentially leading to data theft, password harvesting, and lateral movement across the network. The theft of cryptographic keys allows attackers to maintain persistence even after patches are applied (CISA Alert, Bleeping Computer).

Microsoft has released security updates for SharePoint Subscription Edition (KB5002768), SharePoint 2019 (KB5002754), and SharePoint 2016 (KB5002760). Organizations should immediately apply these patches and rotate their SharePoint server ASP.NET machine keys. For systems that cannot be immediately patched, Microsoft recommends configuring Antimalware Scan Interface (AMSI) integration in SharePoint and deploying Microsoft Defender AV on all SharePoint servers. If AMSI cannot be enabled, affected servers should be disconnected from the internet until patched (MSRC Blog).

The cybersecurity community has responded with significant concern due to the critical nature of the vulnerability and its widespread exploitation. CISA has added CVE-2025-53770 to its Known Exploited Vulnerabilities (KEV) catalog, requiring federal agencies to take immediate action. Security experts emphasize that this vulnerability particularly impacts government, schools, healthcare organizations, and large enterprises running on-premises SharePoint deployments (The Record, Forbes).