CVE-2026-45462 Overview
CVE-2026-45462 is a stored cross-site scripting (XSS) vulnerability in Microsoft Office SharePoint Server. The flaw exists because SharePoint fails to properly neutralize user-supplied input during web page generation, classified under [CWE-79]. An authenticated attacker can inject script content that executes in a victim's browser session, enabling spoofing attacks across a network. Exploitation requires user interaction and low privileges, and the impact crosses a security scope boundary. The vulnerability affects SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Server 2016 Enterprise.
Critical Impact
Authenticated attackers can inject persistent scripts into SharePoint pages, enabling spoofing, session content manipulation, and credential phishing against collaborating users.
Affected Products
- Microsoft SharePoint Server Subscription Edition
- Microsoft SharePoint Server 2019
- Microsoft SharePoint Server 2016 Enterprise
Discovery Timeline
- 2026-06-09 - CVE-2026-45462 published to NVD
- 2026-06-10 - Last updated in NVD database
- Vendor Advisory - Microsoft Security Update CVE-2026-45462
Technical Details for CVE-2026-45462
Vulnerability Analysis
The vulnerability resides in SharePoint's web page generation logic, where attacker-controlled input is rendered without sufficient encoding or sanitization. SharePoint reflects this input into HTML responses delivered to other users of the site. Because the script executes within the SharePoint origin, it inherits the trust context of the application. An attacker with authenticated access can place malicious payloads into fields that are later rendered to collaborators or site visitors. The result is a spoofing primitive that can impersonate trusted SharePoint UI elements, modify displayed content, or capture data entered by targeted users. The Microsoft advisory tracks this issue as a network-exploitable XSS that requires the victim to interact with attacker-influenced content.
Root Cause
The root cause is improper neutralization of input during web page generation [CWE-79]. SharePoint accepts input through one or more authenticated entry points and emits that input into HTML without escaping characters such as <, >, and ". When the browser parses the response, the injected markup is interpreted as executable script rather than literal text.
Attack Vector
Exploitation proceeds over the network against a SharePoint web frontend. The attacker authenticates with low privileges, submits a crafted payload to a vulnerable input surface, and waits for a victim to load the affected page. The victim's browser executes the script in the SharePoint origin, allowing the attacker to spoof page content, manipulate DOM elements, or redirect actions. The scope change indicates the script can affect resources beyond the originally vulnerable component, such as embedded frames or cross-application UI elements served from the same site collection.
No verified public exploit code is available. The vulnerability manifests when SharePoint renders unsanitized input into HTML responses delivered to authenticated users. See the Microsoft Security Update CVE-2026-45462 advisory for vendor-supplied technical details.
Detection Methods for CVE-2026-45462
Indicators of Compromise
- SharePoint list items, web part properties, or page fields containing <script>, javascript:, or HTML event handler attributes such as onerror= and onload=.
- Unusual outbound requests from user browsers to attacker-controlled domains immediately after loading a SharePoint page.
- Audit log entries showing low-privilege accounts editing fields they do not normally modify.
Detection Strategies
- Inspect SharePoint Unified Logging Service (ULS) logs and content database entries for HTML-encoded or raw script markup in user-editable fields.
- Deploy web application firewall rules that flag XSS payload patterns submitted to SharePoint endpoints under _layouts/, _api/, and list form handlers.
- Correlate authenticated edit events with subsequent anomalous page renderings reported by browser-side error monitoring.
Monitoring Recommendations
- Forward SharePoint IIS, ULS, and audit logs to a centralized analytics platform and alert on suspicious markup tokens in field values.
- Monitor Content Security Policy (CSP) violation reports from user browsers visiting SharePoint sites.
- Track EPSS exposure (0.06%, percentile 19.123) alongside internal exposure metrics to prioritize remediation in customer-facing SharePoint farms.
How to Mitigate CVE-2026-45462
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-45462 to all affected SharePoint Server instances.
- Audit recent edits to lists, pages, and web part properties for embedded script content and remove malicious entries.
- Review SharePoint permissions and remove unnecessary contributor or edit rights from low-trust accounts.
Patch Information
Microsoft has published security updates for SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Server 2016 through the Microsoft Update Guide. Administrators should install the cumulative update that includes the fix for CVE-2026-45462 and restart affected services. Confirm successful deployment using the build numbers listed in the vendor advisory.
Workarounds
- Restrict contributor permissions so only trusted users can submit content to SharePoint lists and pages until patches are applied.
- Enforce a strict Content Security Policy on SharePoint sites to limit inline script execution and reduce XSS impact.
- Enable browser-side XSS protections and require modern browsers that honor CSP directives for all SharePoint users.
# Verify SharePoint build version after patching (run on the SharePoint server)
Get-SPFarm | Select-Object BuildVersion
Get-SPProduct -Local | Select-Object ProductName, PatchableUnitDisplayName, PatchVersion
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
