CVE-2025-59547 is a medium-severity vulnerability affecting versions of the Dnn.Platform (formerly DotNetNuke) content management system prior to 10.1.0. The vulnerability arises from improper handling of Unicode encoding in the CKEditor file upload endpoint. Specifically, the endpoint insufficiently sanitizes filenames containing Unicode characters. When a specially crafted file upload request is made with such Unicode characters, the filename is translated into a path that can be manipulated to probe internal network endpoints. This means an attacker can potentially use the file upload functionality to access or enumerate internal resources within the network hosting the vulnerable Dnn instance. The vulnerability is categorized under CWE-176, which relates to improper handling of Unicode encoding, leading to security issues such as path traversal or information disclosure. The vulnerability does not require authentication or user interaction and can be exploited remotely over the network. The CVSS v3.1 base score is 5.3 (medium), reflecting that the attack vector is network-based with low attack complexity, no privileges or user interaction required, and the impact is limited to confidentiality (information disclosure) without affecting integrity or availability. No known exploits are currently reported in the wild, and the issue has been patched in Dnn.Platform version 10.1.0. Organizations running versions prior to 10.1.0 are at risk if their CKEditor file upload endpoint is exposed to untrusted users or the internet. The vulnerability allows attackers to probe internal network resources, which could facilitate further attacks or reconnaissance within the victim's network environment.

For European organizations using Dnn.Platform versions earlier than 10.1.0, this vulnerability poses a risk of internal network reconnaissance and potential information disclosure. Attackers exploiting this flaw could map internal network endpoints, gaining insights into network architecture, services, or sensitive internal resources. This could be a stepping stone for more advanced attacks such as lateral movement, targeted exploitation of internal services, or data exfiltration. The impact is particularly relevant for organizations hosting sensitive or critical infrastructure websites on Dnn.Platform, including government agencies, healthcare providers, financial institutions, and enterprises with internal web portals. Since the vulnerability does not directly allow code execution or data modification, the immediate impact is limited to confidentiality breaches. However, the exposure of internal network details can significantly increase the attack surface and risk profile. European organizations with strict data protection regulations (e.g., GDPR) must consider the potential compliance implications of any unauthorized internal information disclosure. Additionally, organizations with segmented networks relying on obscurity for internal resource protection may find this vulnerability undermines that security assumption.

1. Upgrade Dnn.Platform to version 10.1.0 or later immediately, as this version contains the official patch addressing the Unicode filename sanitization issue. 2. Restrict access to the CKEditor file upload endpoint by implementing network-level controls such as IP whitelisting, VPN access, or web application firewall (WAF) rules to limit exposure to trusted users only. 3. Implement strict input validation and sanitization on file uploads, ensuring filenames do not contain unexpected Unicode characters or path traversal sequences. 4. Monitor web server logs for unusual file upload requests containing Unicode or suspicious patterns that could indicate probing attempts. 5. Conduct internal network segmentation and hardening to reduce the impact of any internal reconnaissance, ensuring that sensitive internal endpoints are not directly accessible from web-facing servers. 6. Employ runtime application self-protection (RASP) or intrusion detection systems (IDS) to detect and block exploitation attempts targeting the file upload functionality. 7. Educate development and operations teams about secure handling of Unicode and input sanitization best practices to prevent similar vulnerabilities in custom or third-party components.