Critical Microsoft SharePoint Vulnerability: CVE-2025-53770 Explained

CVE-2025-53770 is a critical remote code execution vulnerability affecting Microsoft SharePoint Server. Microsoft disclosed it in mid-2025 and rated it Critical with a CVSS score that put it among the most serious SharePoint vulnerabilities in recent years. This article explains what the vulnerability is, who is affected, what the patch status is, and what SharePoint administrators need to do.

What Is CVE-2025-53770?

CVE-2025-53770 is a remote code execution (RCE) vulnerability in Microsoft SharePoint Server. A remote code execution vulnerability means that an attacker who successfully exploits it can run arbitrary code on the affected server, potentially with the same permissions as the SharePoint service account. In a SharePoint environment, this could allow an attacker to access, modify, or delete data, move laterally within the network, or install malware.

The vulnerability was classified as pre-authentication or required low-level authentication in some variants, meaning it could potentially be exploited without the attacker having a valid SharePoint account, which significantly raises the severity.

Which SharePoint Versions Are Affected?

CVE-2025-53770 affects SharePoint Server on-premises deployments. Microsoft's security advisory identifies the affected versions. At the time of disclosure, the affected versions included SharePoint Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition. Specific affected builds and the fixed build numbers are listed in the official Microsoft Security Response Center (MSRC) advisory.

SharePoint Online, which is the cloud-hosted version of SharePoint as part of Microsoft 365, is not affected by this vulnerability. Microsoft manages patching for SharePoint Online and addressed any related issues on the service side before public disclosure.

Is This Being Actively Exploited?

At the time of disclosure, Microsoft indicated the vulnerability had been disclosed publicly, which typically increases the risk of exploitation even if active exploitation had not been widely observed at that point. For critical RCE vulnerabilities in widely deployed server software like SharePoint, the window between public disclosure and active exploitation attempts is often short. Organizations running unpatched SharePoint Server should treat this as urgent.

Potential Impacts

• Remote Code Execution: Full server compromise without authentication.
• Persistent Access: Attackers maintain server access post-patch through stolen keys.
• Data Compromise: Potential for data theft, manipulation, or deletion.
• Extended Risk: Compromise could spread to other integrated Microsoft services.

How to Mitigate and Recover from CVE-2025-53770

Immediate actions include:

1. Patch Your SharePoint Servers Immediately
   • Microsoft released patches for SharePoint 2019 and Subscription Edition in July 2025.
   • Patch release for SharePoint 2016 is forthcoming; monitor official Microsoft channels for updates.
2. Enable Enhanced Protection Measures
   • Activate AMSI (Antimalware Scan Interface).
   • Deploy Microsoft Defender Antivirus or similar solutions on all servers.
3. Rotate Security Keys
   • Change your SharePoint Server ASP.NET MachineKeys immediately after patching.
4. Network Access Control
   • Temporarily isolate or limit access to your SharePoint servers from external networks.
   • Restrict server access to only trusted IP addresses.
5. Monitoring and Threat Detection
   • Closely monitor network traffic, especially suspicious POST requests to /_layouts/15/ToolPane.aspx?DisplayMode=Edit.
   • Implement network defenses, such as Web Application Firewalls (WAF) and Intrusion Prevention Systems (IPS).
6. Conduct Post-Incident Audits
   • Thoroughly investigate for possible backdoors, unusual activity in IIS processes, or unauthorized changes.
7. Threat Intelligence and Scanning
   • Use vulnerability scanning tools (like Qualys) to detect this vulnerability and potential compromises.
8. Report Incidents Promptly
   • If compromised, report to cybersecurity authorities such as CISA immediately.

Why SharePoint RCE Vulnerabilities Are Serious

SharePoint servers frequently hold sensitive organizational data including HR documents, financial files, project materials, and internal communications. They also sit inside the corporate network where they have access to other internal systems. A successful RCE exploit on SharePoint can be the starting point for lateral movement across an entire organization.

Critical SharePoint RCE vulnerabilities have been exploited in real-world attacks before. CVE-2019-0604 and CVE-2022-29108 are historical examples where unpatched SharePoint servers were used as initial access points in significant compromises. The pattern repeats, which is why rapid patching is essential.

Frequently Asked Questions

Do I need to patch all servers in the farm or just the application server?

All servers in the SharePoint farm need to be patched, including all web front ends, application servers, and any other servers running SharePoint components. Leaving any server unpatched means the vulnerability remains exploitable through that server.

Can I just take the SharePoint site offline temporarily instead of patching?

Taking the site offline reduces the attack surface but is not a substitute for patching. If the server is on a network reachable by any internal or external threat, it remains at risk even if the web site itself is down. Patch as quickly as your change management process allows.

Where can I find the official Microsoft advisory?

Go to msrc.microsoft.com and search for CVE-2025-53770. The official advisory includes the affected versions, severity score, links to the security updates, and any mitigations or workarounds Microsoft has identified. Always use the MSRC advisory as your source of truth rather than third-party summaries, which may be incomplete or out of date.

CVE-2025-53770 represents an urgent and critical risk for organizations using affected SharePoint servers. Immediate patching, monitoring, and implementing security measures are essential to mitigate this threat.

For the latest updates and detailed guidance, check the following sources:

• Microsoft - Keep checking as guidance may continue to be updated.
• CISA -Report if it has been found your systems are compromised.
• Eye Security - Identified large scale exploitation of this zero-day.

Stay informed and take swift, appropriate actions to protect your systems.