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CVE-2026-47640 is a cross-site scripting (XSS) vulnerability in Microsoft Office SharePoint. It arises from improper neutralization of user-supplied input during web page generation, a weakness classified as CWE-79. An authenticated attacker can exploit this flaw to inject malicious scripts into SharePoint pages. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), and low privileges (PR:L). User interaction (UI:R) is required, and the scope is unchanged (S:U). The CVSS 3.1 base score is 4.6 (MEDIUM), with low impacts on confidentiality (C:L) and integrity (I:L). Availability is not affected.
The vulnerability occurs when SharePoint fails to properly sanitize input before rendering it in a web page. An attacker with authorized access (e.g., a low-privileged user) can inject a crafted payload into a page, such as a wiki page, web part, or custom field. When another user views the compromised page, the payload executes in their browser context, allowing the attacker to spoof content, redirect the victim to malicious sites, or present forged login forms. This spoofing can erode trust and lead to credential theft or other client-side attacks.
The vulnerability affects Microsoft SharePoint Server 2016, 2019, and Subscription Edition, with specific builds such as 16.0.5548.1003 and 16.0.5552.1002 being confirmed vulnerable. The impact is limited to authenticated users who have access to the SharePoint environment. While the CVSS score indicates moderate risk, the practical impact can be higher if the spoofing is used as part of a phishing campaign or combined with other vulnerabilities. Microsoft released a patch as part of the June 2026 security update cycle. Administrators of on-premises farms should prioritize applying the update to prevent potential exploitation.
DailyCVE Form:
Platform: SharePoint Server
Version: 2016/2019/Sub. Ed.
Vulnerability : Cross-Site Scripting
Severity: MEDIUM (CVSS 4.6)
date: June 9, 2026
Prediction: Patch June 9, 2026
What Undercode Say:
Analytics:
Check SharePoint build version
(Get-SPFarm).BuildVersion.ToString()
Search for XSS patterns in SharePoint logs
Select-String -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\LOGS.log" -Pattern "alert(" -CaseSensitive
Apply the security update (example for SharePoint 2019)
Download the update from Microsoft Update Catalog or use Windows Update
Install with administrative privileges
msiexec /p "sts2019-kb5001234-fullfile-x64-glb.msp" /quiet /norestart
Verify patch installation
Get-HotFix | Where-Object {$_.HotFixID -like "KB5001234"}
Exploit:
An authenticated attacker crafts a malicious payload, such as <script>alert('XSS')</script>, and injects it into a SharePoint page via a vulnerable input field. When another user accesses the page, the script executes, enabling session spoofing or credential phishing.
Protection:
- Apply Microsoft’s June 2026 security update immediately.
- Restrict edit permissions for pages and web parts.
- Enable SharePoint’s built-in XSS filtering and HTML sanitization.
- Monitor logs for suspicious script injection attempts.
- Implement Content Security Policy (CSP) headers.
Impact:
An attacker can spoof legitimate SharePoint content, potentially tricking users into revealing credentials or clicking malicious links. This undermines trust in the platform and can be used as a stepping stone for further attacks, such as privilege escalation or lateral movement within an enterprise network.
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Sources:
Reported By: nvd.nist.gov
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