Microsoft SharePoint Server Under Attack: Critical RCE Vulnerability Exploited in the Wild
Thousands of organizations worldwide are facing immediate cybersecurity threats as Microsoft confirms active exploitation of a critical remote code execution (RCE) vulnerability in SharePoint Server. This security flaw allows attackers to bypass authentication and establish persistent backdoor access to on-premise SharePoint environments, with compromised systems remaining vulnerable even after applying Microsoft’s official patches.
The Severity of the SharePoint RCE Vulnerability
Security researchers have classified this SharePoint vulnerability as critical due to its combination of high impact and low attack complexity. Unlike many server vulnerabilities that require privileged access, this flaw enables unauthenticated attackers to execute arbitrary code with SYSTEM-level permissions. Microsoft’s threat intelligence team has observed multiple attack groups weaponizing this vulnerability since its discovery, with exploitation attempts increasing by 217% in the past 30 days according to recent telemetry data.
How the Attack Works
Attackers are exploiting a deserialization vulnerability in SharePoint’s document conversion service. The attack chain typically follows this pattern:
1. Initial Compromise: Attackers send specially crafted requests to vulnerable SharePoint servers
2. Payload Delivery: Malicious code executes during document processing operations
3. Persistence Establishment: Attackers deploy web shells or other backdoors
4. Lateral Movement: Compromised servers are used to pivot through corporate networks
Recent case studies show attackers maintaining access for an average of 47 days before detection, with some advanced persistent threat (APT) groups using the vulnerability as an initial entry point for ransomware deployment.
Affected Versions and Patch Status
Microsoft has released security updates for the following vulnerable SharePoint versions:
– SharePoint Server 2019 (All cumulative updates prior to August 2023)
– SharePoint Server 2016 (Service Pack 2 with certain configurations)
– SharePoint Server 2013 (Extended support versions only)
Despite available patches, Microsoft warns that simply applying updates may not remove existing compromises. The company’s security advisory notes that over 35% of patched systems in their testing environment still showed evidence of residual attacker presence.
Detection and Mitigation Strategies
Organizations must implement a multi-layered defense approach:
Immediate Actions:
– Apply the latest SharePoint security updates (KB5002231 and later)
– Conduct forensic analysis of all SharePoint servers
– Rotate all credentials that may have been exposed
– Review authentication logs for suspicious activity
Advanced Protection Measures:
– Implement network segmentation for SharePoint servers
– Enable enhanced logging for document conversion services
– Deploy web application firewalls with specific SharePoint protection rules
– Configure real-time monitoring for suspicious PowerShell activity
Microsoft Defender for Office 365 has added new detection rules (SHA-256 hashes available in their security center) to identify known attack patterns associated with this vulnerability.
Global Impact and Industry-Specific Risks
The widespread adoption of SharePoint across multiple industries makes this vulnerability particularly dangerous. Security firm Rapid7 estimates that over 120,000 internet-facing SharePoint servers may be vulnerable worldwide, with particular concentration in:
– Financial services (23% of vulnerable instances)
– Healthcare organizations (18%)
– Government agencies (15%)
– Educational institutions (12%)
Recent attacks have shown industry-specific payloads, including:
– Banking trojans targeting financial sector SharePoint deployments
– Patient data exfiltration tools in healthcare environments
– Ransomware tailored for municipal government systems
The Cost of Inaction
Failure to address this vulnerability can lead to severe consequences:
– Data breaches averaging $4.45 million per incident (IBM 2023 Cost of Data Breach Report)
– Regulatory fines up to €20 million under GDPR for European organizations
– Business disruption costs exceeding $300,000 per day for mid-sized enterprises
Long-Term Security Recommendations
Beyond immediate patching, organizations should:
1. Implement Zero Trust Architecture for SharePoint access
2. Conduct regular penetration testing of collaboration platforms
3. Establish immutable backups of critical SharePoint data
4. Train IT staff on advanced SharePoint security hardening techniques
5. Subscribe to Microsoft’s security notification service for real-time alerts
Third-Party Security Solutions
Several cybersecurity vendors have released additional protection layers:
– CrowdStrike Falcon Overwatch: Added specialized SharePoint monitoring
– Palo Alto Networks Prisma Cloud: New SharePoint-specific rulesets
– Trend Micro Deep Security: Virtual patching for unpatched systems
– Qualys Vulnerability Management: Enhanced SharePoint scanning
Case Study: Fortune 500 Company Attack
A recent incident at a multinational corporation illustrates the attack’s sophistication:
– Initial compromise through SharePoint vulnerability
– Lateral movement to Active Directory servers
– Data exfiltration over 28 days
– Final ransomware payload affecting 12,000 endpoints
The company reported $8.7 million in total damages, including:
– $3.2 million in ransom payment
– $2.1 million in recovery costs
– $3.4 million in business interruption
FAQ Section
Q: How can I check if my SharePoint server is vulnerable?
A: Microsoft provides a PowerShell script (Get-SPProductVersion) to verify patch levels. Security teams should also review the Microsoft Security Advisory for specific version information.
Q: Are cloud-based SharePoint Online instances affected?
A: No, this vulnerability only impacts on-premises SharePoint Server deployments. Microsoft 365 customers are not affected.
Q: What are the indicators of compromise to look for?
A: Key indicators include unexpected files in the _layouts/15 directory, unusual process execution from the SharePoint timer service, and anomalous network connections from SharePoint servers.
Q: How long does remediation typically take?
A: Full remediation including forensic analysis averages 14-21 days for mid-sized organizations according to incident response firms.
Q: Are there any known false positives in detection?
A: Some legitimate document conversion operations may trigger alerts. Microsoft provides guidance on distinguishing between normal and malicious activity in their technical documentation.
Proactive Defense Checklist
To protect against current and future SharePoint vulnerabilities:
1. Enable automatic updates for all SharePoint components
2. Restrict internet-facing SharePoint servers
3. Implement privileged access management
4. Conduct regular security configuration reviews
5. Maintain an incident response plan specific to collaboration platforms
Microsoft has emphasized that this vulnerability represents one of the most severe threats to enterprise collaboration systems in recent years. With attackers actively scanning for vulnerable systems, immediate action is critical for all organizations running on-premises SharePoint deployments.
For organizations lacking internal security expertise, Microsoft recommends engaging with their certified security partners for rapid response services. The company has also established a priority support channel for enterprises dealing with active compromises related to this vulnerability.
Security professionals should monitor the CVE database and Microsoft’s security advisories for emerging variants of this attack, as researchers have already identified potential modifications being tested in the wild. The evolving nature of these exploits underscores the need for continuous monitoring rather than one-time patching.
Explore our enterprise security solutions for comprehensive protection against SharePoint vulnerabilities and other critical threats. Contact our security experts today for a free vulnerability assessment of your collaboration infrastructure.