CVE-2024-38094: Microsoft SharePoint Deserialization Vulnerability

CVE-2024-38094 is a deserialization vulnerability in Microsoft SharePoint that enables remote code execution. Attackers who can reach a vulnerable SharePoint instance may run arbitrary code on the underlying server, which can lead to full system compromise, data theft, or further lateral movement. CISA notes that this issue has been used by ransomware operators, so organizations running SharePoint should treat it as a high-priority risk and confirm current status against the vendor advisory.

How it works

The flaw belongs to CWE-502 (Deserialization of Untrusted Data). SharePoint processes serialized objects; when those objects come from an untrusted source and are not properly validated, an attacker can craft malicious input that the application deserializes into executable objects. Successful abuse results in remote code execution under the privileges of the SharePoint process. Exact request formats, endpoints, or payload construction are not detailed in the public summary and must be verified against Microsoft’s advisory; defenders should assume any unauthenticated or low-privilege network access to SharePoint services could be sufficient for exploitation of this class of issue.

Am I affected? How to find it in your systems

Microsoft SharePoint is commonly deployed as on-premises server farms, hybrid configurations, or SharePoint Server instances supporting collaboration, document management, and intranet portals. Inventory every SharePoint installation by querying Active Directory for SharePoint-related service accounts, scanning for the SharePoint Central Administration site, reviewing installed Microsoft server products via inventory tools, and examining web-server roles that host SharePoint web applications.

• Confirm the exact product edition and build against the vendor advisory; public detail does not list specific version ranges here.
• Check configuration for any custom web parts, workflows, or third-party solutions that perform object serialization.
• Review IIS and SharePoint ULS logs for anomalous POST requests, unexpected deserialization exceptions, or process creation events originating from the SharePoint worker process (w3wp.exe or similar).
• Look for telemetry indicators such as unusual child processes spawned by SharePoint services, sudden outbound connections, or ransomware-related file encryption activity on SharePoint content databases or file shares.

Any SharePoint environment reachable from untrusted networks should be treated as potentially exposed until proven otherwise.

How to remediate

Apply the security update provided by Microsoft for this CVE as the primary remediation. Follow the vendor’s installation guidance exactly, including any required restarts or configuration steps. After patching, verify the update is present by checking the product’s build number or update history against the advisory.

• Disable or remove any unused SharePoint features, web services, or custom code that perform deserialization.
• Enforce least-privilege service accounts for SharePoint application pools and restrict their ability to spawn new processes or write to sensitive locations.
• Ensure SharePoint servers are fully patched for related Microsoft components and that the farm is not running with elevated or unnecessary privileges.
• If mitigations are unavailable or the product cannot be updated, CISA directs organizations to discontinue use of the product.

If you can't patch immediately

Until the vendor update can be applied, reduce exposure with compensating controls:

• Segment SharePoint servers onto isolated network segments; allow only necessary management and client traffic through tightly scoped firewall rules or network ACLs.
• Place a web application firewall (WAF) or reverse proxy in front of SharePoint and enable rules that block or alert on anomalous serialized payloads and known attack patterns for deserialization flaws; treat this as virtual patching only.
• Temporarily disable non-essential SharePoint services, remote interfaces, or features that accept complex object input if the business can tolerate the loss of functionality.
• Increase monitoring: forward SharePoint, IIS, and Windows security logs to a SIEM; alert on process creation from SharePoint binaries, unexpected PowerShell or cmd.exe activity, and file modifications outside normal content libraries.
• Restrict administrative access to SharePoint Central Administration and require multi-factor authentication for all privileged accounts.

These measures lower risk but do not eliminate it; schedule the official patch as soon as possible.

If your data may have been exposed

Actively exploited vulnerabilities of this type frequently lead to ransomware deployment and data breaches. If compromise is suspected, isolate affected servers, preserve forensic evidence, and follow your incident-response plan. Organizations can also run a free exposure scan of their email addresses against known breach data sets to determine whether credentials or other information associated with the environment have already appeared in public dumps.