CVE-2015-2526 in .NET Framework
Summary
by MITRE
Microsoft .NET Framework 4.5, 4.5.1, 4.5.2, and 4.6 allows remote attackers to cause a denial of service to an ASP.NET web site via crafted requests, aka "MVC Denial of Service Vulnerability."
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 06/14/2022
The CVE-2015-2526 vulnerability represents a critical denial of service flaw within Microsoft's .NET Framework versions 4.5, 4.5.1, 4.5.2, and 4.6 that specifically affects ASP.NET web applications utilizing the Model-View-Controller architectural pattern. This vulnerability stems from improper handling of crafted HTTP requests that can trigger excessive resource consumption within the web application's processing pipeline, ultimately leading to service unavailability for legitimate users. The flaw operates at the application layer and can be exploited remotely without authentication, making it particularly dangerous for publicly accessible web services. Security researchers identified that when an ASP.NET MVC application processes malformed requests containing specific patterns in URL parameters or query strings, the framework's routing engine becomes susceptible to resource exhaustion attacks that can effectively crash the application or render it unresponsive to legitimate traffic.
The technical root cause of this vulnerability lies in the insufficient input validation and resource management within the ASP.NET MVC routing component of the affected .NET Framework versions. When processing specially crafted requests, the framework's internal mechanisms for parsing and routing URL segments fail to properly limit resource consumption during request processing, leading to a condition where malicious inputs can cause the application to consume excessive memory or CPU cycles. This behavior aligns with CWE-400, which categorizes "Uncontrolled Resource Consumption" as a fundamental weakness in software design that can lead to denial of service conditions. The vulnerability specifically targets the MVC framework's handling of route data and parameter binding, where attackers can construct requests that force the application to perform computationally expensive operations or allocate excessive memory resources. The flaw demonstrates characteristics consistent with the ATT&CK technique T1499.004, which describes "Network Denial of Service" through resource exhaustion attacks that consume system resources and prevent legitimate users from accessing services.
The operational impact of CVE-2015-2526 extends beyond simple service disruption to potentially compromise the entire web application infrastructure and affect business continuity for organizations relying on ASP.NET MVC applications. Attackers can leverage this vulnerability to consume system resources rapidly, causing the web server to become unresponsive or crash entirely, resulting in significant downtime for affected services. The vulnerability affects organizations running Microsoft IIS web servers with ASP.NET MVC applications, particularly those that process user-supplied URL parameters without proper validation. The attack vector is particularly concerning because it requires no authentication and can be executed through standard web browser interactions or automated tools, making it accessible to a wide range of threat actors. Organizations with high-traffic web applications face the greatest risk, as the vulnerability can be exploited to cause cascading failures across multiple application instances or entire server farms. The impact is exacerbated when applications are configured to use default settings or lack proper input sanitization measures, as these configurations provide minimal protection against the resource exhaustion patterns exploited by this vulnerability.
Mitigation strategies for CVE-2015-2526 primarily involve applying Microsoft's official security patches and updates to the affected .NET Framework versions, which address the underlying resource consumption issues in the MVC routing engine. Organizations should prioritize immediate deployment of the relevant security updates from Microsoft's security bulletin MS15-050, which specifically addresses this vulnerability. Additionally, implementing proper input validation and sanitization measures at the application level can provide defense-in-depth protection against exploitation attempts. Security controls should include rate limiting mechanisms, request size restrictions, and monitoring for unusual resource consumption patterns that could indicate exploitation attempts. Network-level protections such as web application firewalls can help detect and block malicious requests before they reach the vulnerable application components. Organizations should also consider implementing application-level safeguards that monitor for excessive memory allocation or CPU usage patterns that correlate with the exploitation behavior of this vulnerability. Regular security assessments and penetration testing should be conducted to verify that the implemented mitigations are effective and that no additional attack vectors remain unaddressed. The remediation process must include thorough testing of patches in staging environments to ensure compatibility and prevent unintended side effects on existing application functionality.