Fulcrum Response to Critical SharePoint Vulnerability (CVE-2025-53770)

CRITICAL ALERT: Threat actors are actively exploiting a 0-day vulnerability in Microsoft SharePoint

Microsoft just created CVE-2025-53770 (CVSS 9.8) to track a new unpatched critical vulnerability that's being actively exploited in the wild. Microsoft hasn't yet released a security patch, but they published emergency mitigation guidance. This threat campaign is active and evolving, with more details expected in the coming days.

What You Need to Know Right Now

• If your organization has on-premises Microsoft SharePoint exposed to the internet, you have urgent homework to do

• This isn't an "apply the patch and you're done" situation - organizations need to implement mitigations immediately, assume compromise, and investigate whether systems were compromised prior to mitigation

• Microsoft will likely release an emergency out-of-cycle patch due to the broad exploitation currently underway

• Only on-premises SharePoint is affected - SharePoint Online in Microsoft 365 is not impacted

  
  

Microsoft's Uniquely Urgent Guidance

1. Configure Windows Antimalware Scan Interface (AMSI) integration in SharePoint and deploy Defender AV (or another EDR solution)

2. Disconnect Microsoft SharePoint from the internet until a patch is available or the above can be implemented

   
   

How Fulcrum Can Help

Emergency Response Services

• Immediate vulnerability assessment of your SharePoint environment

• Rapid implementation of Microsoft's emergency mitigations (AMSI configuration and EDR deployment)

• Network isolation assistance to safely disconnect SharePoint from internet exposure

• 24/7 incident response support through our MSSP SOC team

Comprehensive Security Review

• Forensic investigation to determine if systems were previously compromised

• SharePoint security hardening beyond the immediate vulnerability

• Attack simulation testing to validate your defenses against SharePoint-targeted threats

• Complete infrastructure assessment to identify other potential exposure points

Long-term Protection Strategy

• Managed security services for ongoing SharePoint monitoring and protection

• Patch management to ensure rapid deployment when Microsoft releases the fix

• Security architecture review to reduce future attack surface

• Staff training on SharePoint security best practices

Why Choose Fulcrum

Our security experts have extensive experience with Microsoft SharePoint environments and enterprise incident response. We understand the urgency of this situation and can mobilize our team immediately to:

• Deploy emergency mitigations within hours, not days

• Provide expert guidance without vendor lock-in to specific security tools

• Leverage our established relationships with Microsoft for the latest threat intelligence

• Ensure minimal business disruption during remediation

Take Action Now

Time is critical. Contact Fulcrum immediately if your organization operates on-premises SharePoint systems, especially those accessible from the internet.

Email: info@ftsc.com

Don't wait for a patch that may be days or weeks away. Let Fulcrum help secure your environment today.

References

• Customer guidance for SharePoint vulnerability CVE-2025-53770

• Microsoft Releases Guidance on Exploitation of SharePoint Vulnerability (CVE-2025-53770)