Urgent Cybersecurity Alert: Active Exploitation of SharePoint Zero-Day Vulnerability CVE-2025-53770

In recent days, a significant cybersecurity threat has emerged targeting Microsoft SharePoint servers, a critical platform for document management and collaboration within organizations. This zero-day vulnerability, identified as CVE-2025-53770, has been actively exploited, prompting urgent responses from Microsoft, the FBI, and cybersecurity agencies worldwide.

Understanding the Vulnerability​

CVE-2025-53770 is a remote code execution (RCE) vulnerability affecting on-premises SharePoint Server installations. This flaw allows unauthenticated attackers to execute arbitrary code over a network, potentially leading to full system compromise. Notably, SharePoint Online, part of Microsoft 365's cloud services, remains unaffected by this vulnerability. (msrc.microsoft.com)
The vulnerability stems from the deserialization of untrusted data within SharePoint servers, enabling attackers to exploit the system without prior authentication. This type of attack can lead to unauthorized access, data exfiltration, and further network infiltration. (cyber.gc.ca)

Scope and Impact​

The exploitation of CVE-2025-53770 has been widespread, affecting numerous organizations globally. Reports indicate that both U.S. federal and state agencies, as well as international businesses, have been compromised. The Washington Post highlighted that tens of thousands of servers are at risk, with attackers gaining access to sensitive documents and internal configurations. (washingtonpost.com)
Security researchers have observed attackers installing web shells and exfiltrating cryptographic secrets from victim servers, granting persistent, unauthenticated access and posing significant risks to affected organizations. (securityweek.com)

Microsoft's Response and Recommendations​

In response to the active exploitation, Microsoft has issued guidance to mitigate the threat. As of now, a security patch is not yet available; however, Microsoft recommends the following immediate actions:

• Enable AMSI Integration: Configure Antimalware Scan Interface (AMSI) integration in SharePoint Server to detect and block malicious activities.
• Deploy Microsoft Defender Antivirus: Ensure that Microsoft Defender Antivirus is active on all SharePoint servers to provide real-time protection.
• Disconnect from the Internet: If enabling AMSI is not feasible, consider disconnecting the server from the internet until a security update is available.
• Implement Defender for Endpoint: Deploy Microsoft Defender for Endpoint to detect and block post-exploit activities.

These measures aim to prevent unauthenticated attackers from exploiting the vulnerability and to protect organizational data. (msrc.microsoft.com)

Broader Implications​

This incident underscores the critical importance of timely patch management and proactive cybersecurity measures. Organizations relying on on-premises solutions must remain vigilant, as such systems can become prime targets for attackers exploiting unpatched vulnerabilities.
The rapid exploitation of CVE-2025-53770 highlights the evolving nature of cyber threats and the necessity for organizations to adopt a comprehensive security posture. This includes regular system updates, continuous monitoring, and the implementation of advanced threat detection mechanisms.

Conclusion​

The active exploitation of the SharePoint vulnerability CVE-2025-53770 serves as a stark reminder of the persistent and evolving threats in the cybersecurity landscape. Organizations must act swiftly to implement Microsoft's recommended mitigations and remain alert for further updates. Maintaining robust security practices and staying informed about emerging vulnerabilities are essential steps in safeguarding sensitive information and ensuring operational continuity.

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Source: Free Malaysia Today Microsoft alerts businesses, governments to server software attack