High-Severity XSS in DNN CMS Demands Immediate Patching
The National Vulnerability Database has disclosed CVE-2026-40321, a high-severity cross-site scripting (XSS) vulnerability impacting DNN (formerly DotNetNuke) web content management systems prior to version 10.2.2. This flaw allows an attacker to upload a specially crafted SVG file containing malicious scripts. These scripts can then target both authenticated and unauthenticated users accessing the DNN instance.
The impact of this vulnerability, rated with a CVSS score of 8 (HIGH), escalates significantly if the malicious script is executed by a power user. The National Vulnerability Database attributes this to CWE-87, highlighting improper neutralization of input during web page generation. This isn’t theoretical; SVG files are often overlooked as an attack vector, making this a prime candidate for client-side compromise.
Defenders running DNN must prioritize patching to version 10.2.2 immediately. Ignoring this leaves your users, especially those with elevated privileges, exposed to client-side attacks that can lead to session hijacking, data exfiltration, or further compromise of the web application.
What This Means For You
- If your organization uses DNN (DotNetNuke) CMS, you need to verify your version immediately. Patch to version 10.2.2 or later to mitigate CVE-2026-40321. Audit your web logs for any suspicious SVG file uploads or unusual client-side activity, especially around user sessions.
Related ATT&CK Techniques
🛡️ Detection Rules
3 rules · 6 SIEM formats3 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
DNN CVE-2026-40321 SVG File Upload - Free Tier
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2026-40321 | XSS | DNN (DotNetNuke) prior to version 10.2.2 |
| CVE-2026-40321 | XSS | Specially crafted SVG file upload |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | April 18, 2026 at 01:16 UTC |
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