CVE-2025-64672: Microsoft SharePoint Server XSS Vulnerability

CVE-2025-64672 Overview

CVE-2025-64672 is a critical cross-site scripting (XSS) vulnerability affecting Microsoft Office SharePoint Server. The vulnerability stems from improper neutralization of input during web page generation (CWE-79), which allows an authorized attacker to perform spoofing attacks over a network. This flaw enables attackers to inject malicious scripts into web pages viewed by other users, potentially leading to session hijacking, credential theft, or further exploitation of the SharePoint environment.

Critical Impact

This XSS vulnerability in Microsoft SharePoint Server allows authenticated attackers to execute arbitrary scripts in victim browsers, potentially compromising sensitive enterprise data and enabling lateral movement within organizations relying on SharePoint for collaboration.

Affected Products

• Microsoft SharePoint Server (Subscription Edition)
• Microsoft SharePoint Server (all versions matching cpe:2.3:a:microsoft:sharepoint_server:::::subscription:::*)

Discovery Timeline

• 2025-12-09 - CVE-2025-64672 published to NVD
• 2025-12-12 - Last updated in NVD database

Technical Details for CVE-2025-64672

Vulnerability Analysis

This cross-site scripting vulnerability exists in Microsoft SharePoint Server due to improper neutralization of user-supplied input before it is included in dynamically generated web pages. When a SharePoint page processes user input without adequate sanitization, an attacker can craft malicious payloads that execute arbitrary JavaScript code in the context of authenticated users' sessions.

The attack requires the attacker to be authenticated to the SharePoint environment, but once authenticated, they can leverage this vulnerability to target other users. The scope is changed (S:C in the CVSS vector), meaning the vulnerability can affect resources beyond the vulnerable component itself, impacting the confidentiality and integrity of data across the broader SharePoint deployment.

Root Cause

The root cause of CVE-2025-64672 is improper input validation and output encoding in Microsoft SharePoint Server's web page generation functionality. When user-controlled data is rendered in HTML context without proper sanitization or encoding, it creates an injection point for malicious scripts. This is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation).

Attack Vector

The attack vector is network-based, requiring an authenticated attacker to inject malicious content that will be rendered to other users. The exploitation requires user interaction from the victim (such as clicking a crafted link or viewing a compromised page), but the low attack complexity makes this vulnerability particularly dangerous in enterprise environments where SharePoint is widely used for collaboration and document management.

The attacker could potentially:

• Steal session cookies and authentication tokens
• Perform actions on behalf of victim users
• Redirect users to malicious websites
• Deface SharePoint pages or inject phishing content
• Exfiltrate sensitive data accessible to the victim user

Detection Methods for CVE-2025-64672

Indicators of Compromise

• Unusual JavaScript payloads in SharePoint page content or URL parameters containing encoded script tags
• Unexpected outbound requests from SharePoint servers to external domains
• User reports of suspicious redirects or unexpected behavior when accessing SharePoint pages
• Anomalous session activity indicating potential session hijacking

Detection Strategies

• Implement web application firewall (WAF) rules to detect XSS payload patterns in requests to SharePoint servers
• Enable and monitor SharePoint audit logs for suspicious content modifications or access patterns
• Deploy endpoint detection solutions capable of identifying malicious script execution in browser contexts
• Use SentinelOne's behavioral AI to detect anomalous activity patterns associated with XSS exploitation

Monitoring Recommendations

• Monitor SharePoint ULS logs for error patterns that may indicate exploitation attempts
• Track changes to SharePoint page content for unauthorized script injections
• Review HTTP request logs for suspicious encoding patterns or script-like content in parameters
• Implement alerting for unusual cross-origin requests originating from SharePoint pages

How to Mitigate CVE-2025-64672

Immediate Actions Required

• Apply the latest Microsoft security updates for SharePoint Server immediately
• Review and restrict user permissions to minimize the attack surface from authorized users
• Implement Content Security Policy (CSP) headers to mitigate the impact of successful XSS attacks
• Audit SharePoint content for potentially malicious scripts that may have been injected

Patch Information

Microsoft has released a security update addressing CVE-2025-64672. Administrators should consult the Microsoft Security Response Center advisory for detailed patch information and installation guidance. Apply the security update to all affected SharePoint Server installations as soon as possible.

Workarounds

• Enable HTTP-only and Secure flags on all session cookies to reduce the impact of potential session theft
• Implement strict Content Security Policy headers to limit script execution sources
• Restrict SharePoint user permissions using the principle of least privilege to limit the pool of potential attackers
• Consider enabling additional input validation through custom SharePoint solutions while awaiting patch deployment

# Example: Add Content Security Policy header in IIS for SharePoint
# Open IIS Manager and add the following HTTP Response Header
# Name: Content-Security-Policy
# Value: default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; object-src 'none'

# PowerShell command to check SharePoint patch level
Get-SPFarm | Select-Object BuildVersion