CVE-2026-24838 is a critical vulnerability classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as cross-site scripting (XSS), affecting the Dnn.Platform content management system. DNN is an open-source CMS built on the Microsoft technology stack, widely used for building websites and intranet portals. The vulnerability exists in the handling of module titles that support rich text input, which can include embedded scripts. Prior to versions 9.13.10 and 10.2.0, the platform failed to properly sanitize or neutralize this input, allowing malicious scripts to be stored and executed in the context of the victim’s browser. This stored XSS can be triggered without user interaction once an authenticated user accesses the affected module, potentially allowing attackers to hijack sessions, steal sensitive data, perform actions on behalf of users, or pivot further into the network. The CVSS v3.1 score of 9.1 reflects the vulnerability’s network attack vector, low complexity, requirement for high privileges (authenticated user), no user interaction, and a scope change that impacts confidentiality, integrity, and availability. Although no public exploits have been reported yet, the vulnerability’s nature and severity make it a high-risk issue for organizations relying on vulnerable DNN versions. The fix involves proper input validation and output encoding in module titles, which is included in versions 9.13.10 and 10.2.0.

For European organizations, this vulnerability poses a significant threat, especially those using DNN.Platform for public websites, intranets, or extranets. Successful exploitation can lead to session hijacking, unauthorized data access, defacement, or malware distribution, impacting confidentiality, integrity, and availability of critical web assets. Public sector entities, educational institutions, and enterprises with Microsoft-based infrastructure are particularly at risk due to their adoption of DNN. The vulnerability’s ability to execute scripts in authenticated user contexts can facilitate lateral movement and privilege escalation within corporate networks. Given the critical CVSS score and the potential for widespread impact, organizations face risks of reputational damage, regulatory non-compliance (e.g., GDPR breaches due to data exposure), and operational disruption. The absence of known exploits in the wild currently reduces immediate risk but does not diminish the urgency for remediation.

European organizations should immediately assess their DNN.Platform versions and upgrade to 9.13.10 or 10.2.0 or later to remediate the vulnerability. In addition to patching, organizations should audit all module titles and rich text inputs for malicious content and sanitize or remove suspicious entries. Implement strict role-based access controls to limit who can edit module titles and rich text fields. Employ web application firewalls (WAFs) with custom rules to detect and block XSS payloads targeting DNN modules. Conduct regular security training for administrators to recognize and prevent injection of malicious scripts. Monitor logs for unusual activity indicative of exploitation attempts. Finally, consider deploying Content Security Policy (CSP) headers to mitigate the impact of any residual XSS vulnerabilities.