CVE-2026-24838: DNN (DotNetNuke) XSS Vulnerability

CVE-2026-24838 Overview

CVE-2026-24838 is a Cross-Site Scripting (XSS) vulnerability affecting DNN (formerly DotNetNuke), an open-source web content management platform (CMS) in the Microsoft ecosystem. The vulnerability exists in the module title functionality which supports richtext, allowing the inclusion of malicious scripts that execute in certain scenarios. This stored XSS vulnerability can be exploited by authenticated users with elevated privileges to inject persistent malicious scripts into the CMS.

Critical Impact

Attackers with high-level privileges can inject malicious scripts through module titles, potentially compromising administrator sessions, stealing credentials, or performing unauthorized actions on behalf of other users within the DNN platform.

Affected Products

• DNN Platform versions prior to 9.13.10
• DNN Platform versions prior to 10.2.0
• DNN (DotNetNuke) CMS installations using vulnerable module title richtext functionality

Discovery Timeline

• 2026-01-28 - CVE CVE-2026-24838 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-24838

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting (XSS). The flaw exists in how DNN handles module titles that support richtext content. When richtext is enabled for module titles, the platform fails to properly sanitize or encode user-supplied input before rendering it in the browser context.

The stored nature of this XSS vulnerability makes it particularly dangerous, as malicious payloads persist in the database and execute whenever affected pages are viewed. While exploitation requires high privileges (such as administrator or module editor access), the impact extends beyond the attacker's session—potentially affecting all users who view pages containing the compromised module titles.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and output encoding within the DNN module title processing logic. When richtext support is enabled for module titles, the application accepts HTML content including potentially malicious script tags or event handlers. The platform fails to implement proper content security policies or sanitization routines that would strip or neutralize executable JavaScript code before storing or rendering the content.

Attack Vector

The attack is network-based and requires authenticated access with elevated privileges within the DNN platform. An attacker with the ability to edit module titles can inject malicious JavaScript code disguised as legitimate richtext content. The attack flow involves:

1. An authenticated user with module editing permissions accesses the DNN administration interface
2. The attacker modifies a module title to include malicious script content within the richtext
3. The payload is stored in the database without proper sanitization
4. When any user (including administrators) views a page containing the compromised module, the malicious script executes in their browser context
5. The attacker can steal session tokens, perform actions as the victim, or redirect users to malicious sites

For detailed technical information regarding the exploitation mechanism, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-24838

Indicators of Compromise

• Unusual JavaScript code or event handlers present in module title database fields
• Unexpected network requests originating from DNN pages to external domains
• Administrator or user sessions being hijacked without explanation
• Modified module titles containing <script> tags, onerror, onload, or similar event handler attributes

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect XSS patterns in HTTP requests targeting DNN module management endpoints
• Enable detailed logging for all module title modifications and review for suspicious richtext content
• Deploy SentinelOne Singularity XDR to detect and alert on anomalous script execution patterns within web server processes
• Conduct regular database audits scanning module title fields for known XSS payload signatures

Monitoring Recommendations

• Monitor HTTP request logs for suspicious encoded characters or script injection attempts in module-related API calls
• Configure Content Security Policy (CSP) headers and monitor for CSP violation reports indicating script injection attempts
• Enable SentinelOne's behavioral AI to detect unusual browser-side activity patterns that may indicate successful XSS exploitation
• Set up alerts for any modifications to module titles by users outside of normal change windows

How to Mitigate CVE-2026-24838

Immediate Actions Required

• Upgrade DNN Platform to version 9.13.10 or 10.2.0 or later immediately
• Audit existing module titles in the database for any potentially malicious content
• Review user accounts with module editing privileges and verify their legitimacy
• Implement Content Security Policy (CSP) headers to provide defense-in-depth against script execution

Patch Information

DNN has released security patches in versions 9.13.10 and 10.2.0 that address this vulnerability. The fix implements proper sanitization and encoding of richtext content in module titles, preventing the execution of injected scripts. Organizations should upgrade to these versions or later as soon as possible.

For patch details and upgrade instructions, consult the GitHub Security Advisory.

Workarounds

• Disable richtext support for module titles if the feature is not essential for your deployment
• Implement strict Content Security Policy (CSP) headers with script-src 'self' to block inline script execution
• Restrict module editing privileges to only essential personnel until patching is complete
• Deploy a Web Application Firewall (WAF) with XSS protection rules in front of DNN installations

# Example CSP header configuration for IIS web.config
# Add to <system.webServer><httpProtocol><customHeaders>
# <add name="Content-Security-Policy" value="default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline';" />