Microsoft SharePoint Spoofing Vulnerability due to Improper Input Validation (CVE-2026-32201)

1. Apply Official Security Patches

Deploy the latest Cumulative Updates (CU) and security updates provided by Microsoft immediately.

• Refer to the Microsoft MSRC Update Guide to download and install the appropriate patch for your SharePoint version.

2. Temporary Mitigation (WAF & Monitoring)

If immediate patching is not feasible, configure Web Application Firewall (WAF) rules to inspect and block anomalous HTTP headers and parameter manipulation targeting SharePoint servers.

Example IIS URL Rewrite Rule: You can configure IIS to block suspicious requests with spoofed host headers or parameters:

<system.webServer>
  <rewrite>
    <rules>
      <rule name="Block Suspicious SharePoint Requests" stopProcessing="true">
        <match url=".*" />
        <conditions>
          <!-- Block suspicious external domains or spoofed headers -->
          <add input="{HTTP_HOST}" pattern="^suspicious-external-domain" />
        </conditions>
        <action type="CustomResponse" statusCode="403" statusReason="Forbidden" statusDescription="Access Denied" />
      </rule>
    </rules>
  </rewrite>
</system.webServer>

CVE-2026-32201 is a spoofing vulnerability in Microsoft SharePoint Server caused by improper input validation (CWE-20). An unauthenticated attacker can exploit this vulnerability by sending specially crafted network requests to a vulnerable SharePoint instance, forcing the server to process the request under a spoofed context.

Although assigned a CVSS 3.1 base score of 6.5 (Medium), this vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. With an EPSS score of 0.94 (94%), the likelihood of exploitation is extremely high. The attack vector is network-based (AV:N), requires no privileges (PR:N), and demands no user interaction (UI:N), posing a significant threat to organizational environments.