Unpatched SharePoint Zero-Day Exploited: Urgent Alert for 75+ Global Organizations

A critical, unpatched security vulnerability in Microsoft SharePoint Server is currently under active, large-scale exploitation, leaving over 75 global organizations exposed to data breaches and system compromise. This Zero-Day flaw represents a significant threat to enterprises relying on SharePoint for collaborative workflows and critical data storage. Understanding the nature of this threat and acting swiftly is paramount for IT and security professionals.

The SharePoint Zero-Day: CVE-2025-53770 Explained

The vulnerability, tracked as CVE-2025-53770, carries a severe CVSS score of 9.8, indicating its critical impact and ease of exploitation. Security researchers have identified this as a variant of a previously patched SharePoint vulnerability, CVE-2025-49706. While the earlier flaw, a spoofing bug with a CVSS score of 6.3, was addressed in Microsoft’s July 2025 Patch Tuesday, threat actors have seemingly found a way around the initial fix, weaponizing a closely related variant that bypasses existing defenses.

The active exploitation campaign highlights a sophisticated attack vector, likely targeting the core functionalities of SharePoint Server. Given its nature as a zero-day, no official patch is yet available from Microsoft, making immediate defensive measures crucial for vulnerable organizations.

Impact of Active Exploitation

The active exploitation of CVE-2025-53770 means that attackers are currently able to compromise vulnerable SharePoint Server instances without prior authentication or complex technical maneuvers. The implications are severe:

• Data Breach: Unauthorized access to sensitive corporate documents, intellectual property, and user credentials stored within SharePoint.
• System Compromise: Attackers could execute arbitrary code, establish persistence, and move laterally within the network.
• Disruption of Operations: Malicious activity could lead to service outages, data corruption, or ransomware deployment.
• Reputational Damage: Significant harm to an organization’s trust and standing due to security incidents.

With more than 75 global organizations already reportedly breached, the widespread nature of this campaign underscores the urgency for all SharePoint users to assess their exposure.

Remediation Actions and Mitigation Strategies

As a patch for CVE-2025-53770 is not yet available, organizations must implement proactive and robust mitigation strategies to protect their SharePoint environments:

• Immediate Patching (When Available): Monitor Microsoft security advisories and deploy the official patch for CVE-2025-53770 the moment it is released. Prioritize its deployment given the critical nature.
• Network Segmentation: Isolate SharePoint servers from other critical internal systems to limit potential lateral movement by attackers.
• Principle of Least Privilege: Review and enforce strict access controls for SharePoint administrators and users. Ensure no unnecessary permissions are granted.
• Web Application Firewall (WAF): Implement and configure a WAF in front of SharePoint servers. Leverage its capabilities to detect and block malicious requests, especially those attempting to exploit known or suspected SharePoint vulnerabilities. Regular updates to WAF rulesets are crucial.
• Intrusion Detection/Prevention Systems (IDS/IPS): Ensure IDS/IPS solutions are up-to-date and configured to monitor for unusual traffic patterns or exploit attempts targeting SharePoint services.
• Endpoint Detection and Response (EDR): Deploy EDR solutions on SharePoint servers to detect and respond to suspicious activities at the host level, including unauthorized file access or process execution.
• Vulnerability Scanning and Penetration Testing: Regularly scan SharePoint environments for misconfigurations and vulnerabilities. Conduct periodic penetration tests to simulate attacks and identify weaknesses.
• Secure Configuration Baseline: Adhere to Microsoft’s recommended security baselines for SharePoint Server deployment, disabling unnecessary features and services.
• Regular Backups: Maintain frequent, secure, and offline backups of all SharePoint data to ensure recovery in case of compromise.
• Incident Response Plan: Review and rehearse your incident response plan specifically for critical server compromises. Ensure your team is prepared to detect, contain, eradicate, and recover from a breach.

Recommended Tools for Detection and Mitigation

Leveraging the right security tools can significantly enhance your defensive posture against vulnerabilities like CVE-2025-53770.

Tool Name	Purpose	Link
Microsoft Defender for Endpoint	Endpoint Detection & Response (EDR) for SharePoint servers.	Official Documentation
Azure Application Gateway (with WAF)	Web Application Firewall protecting web applications, including SharePoint.	Official Documentation
Tenable.io / Nessus	Vulnerability scanning for identifying unpatched systems and configurations.	Tenable Nessus
Snort / Suricata	Open-source IDS/IPS for network traffic analysis and threat detection.	Snort / Suricata
Splunk / ELK Stack	Security Information and Event Management (SIEM) for centralized log analysis.	Splunk / ELK Stack

Key Takeaways for Cybersecurity Professionals

The ongoing exploitation of CVE-2025-53770 in Microsoft SharePoint Server underscores several critical aspects of modern cybersecurity:

• Zero-Day Volatility: The rapid weaponization of newly discovered flaws remains a persistent and severe threat. Proactive defense layers are paramount.
• Patch Management Criticality: Even with timely patching (as seen with the variant CVE-2025-49706), attackers are quick to identify and exploit related bypasses or variants.
• Defense-in-Depth: Relying on a single security control is insufficient. A layered security approach, incorporating WAFs, EDR, network segmentation, and regular monitoring, is essential to mitigate unpatched risks.
• Vigilance and Intelligence: Staying informed through credible threat intelligence sources and promptly acting on security advisories is non-negotiable.

Organizations must treat this SharePoint Zero-Day with extreme urgency. Immediate assessment of exposure and implementation of the recommended mitigation strategies are vital to protect critical data and maintain operational integrity.