CVE-2025-3600 is a high-severity vulnerability affecting Progress Software's Telerik UI for ASP.NET AJAX versions from 2011.2.712 up to 2025.1.218. The vulnerability arises from unsafe reflection, specifically the use of externally-controlled input to select classes or code to execute. This unsafe reflection can lead to an unhandled exception that causes the hosting process to crash, resulting in a denial of service (DoS) condition. The vulnerability is categorized under CWE-470, which involves unsafe reflection practices that allow attackers to influence the classes or code loaded by an application. The CVSS v3.1 base score is 7.5, reflecting a high severity due to the network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact is limited to availability, with no direct confidentiality or integrity compromise reported. No known exploits are currently observed in the wild, and no patches have been linked yet. The vulnerability affects a widely used UI component for ASP.NET AJAX applications, which are common in enterprise web applications. Because the flaw causes a crash of the hosting process, attackers can disrupt service availability, potentially affecting business continuity and user experience. The lack of authentication or user interaction requirements makes exploitation relatively straightforward for remote attackers. This vulnerability requires immediate attention to prevent potential denial of service attacks against web applications using the affected Telerik UI versions.

For European organizations, this vulnerability poses a significant risk to the availability of web applications built on Telerik UI for ASP.NET AJAX. Many enterprises and public sector entities in Europe rely on ASP.NET AJAX for internal and customer-facing applications. A successful exploitation could lead to service outages, impacting business operations, customer trust, and regulatory compliance, especially under GDPR where service availability is critical. Denial of service attacks could disrupt critical services such as e-government portals, financial services platforms, and healthcare systems that use Telerik UI components. The absence of confidentiality or integrity impact reduces the risk of data breaches but does not mitigate the operational disruption caused by downtime. Organizations with high availability requirements or those operating in sectors with strict uptime SLAs (e.g., finance, telecommunications) may face reputational damage and financial penalties. Additionally, the ease of exploitation without authentication increases the threat landscape, potentially attracting opportunistic attackers and automated scanning tools targeting European infrastructure.

European organizations should immediately inventory their use of Telerik UI for ASP.NET AJAX to identify affected versions between 2011.2.712 and 2025.1.218. Since no patches are currently linked, organizations should implement temporary mitigations such as: 1) Applying strict input validation and sanitization on any user-supplied data that could influence class or code selection to prevent unsafe reflection triggers. 2) Employing web application firewalls (WAFs) with custom rules to detect and block suspicious requests that attempt to exploit unsafe reflection patterns. 3) Isolating and sandboxing the hosting environment to limit the impact of process crashes and enable rapid recovery. 4) Monitoring application logs and system events for signs of unhandled exceptions or crashes related to Telerik UI components. 5) Planning for rapid patch deployment once official fixes are released by Progress Software. Additionally, organizations should review their incident response plans to handle potential denial of service incidents and ensure backup and failover mechanisms are tested and operational. Engaging with Progress Software support channels for updates and guidance is also recommended.