CVE-2005-1665 in ASP.NET
Summary
by MITRE
The __VIEWSTATE functionality in Microsoft ASP.NET 1.x, when not cryptographically signed, allows remote attackers to cause a denial of service (CPU consumption) via deeply nested markup.
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Analysis
by VulDB Data Team • 07/02/2019
The vulnerability described in CVE-2005-1665 represents a critical security flaw in Microsoft ASP.NET 1.x applications that utilize the __VIEWSTATE functionality without proper cryptographic signing. This issue stems from the way ASP.NET handles view state management for web forms, where the view state is used to maintain the state of server controls across postbacks. When the __VIEWSTATE is not cryptographically signed, it becomes vulnerable to manipulation by remote attackers who can exploit this weakness to consume excessive CPU resources on the affected server.
The technical implementation of this vulnerability occurs within the ASP.NET framework's view state processing mechanism, specifically in how it handles deserialization of view state data. The flaw manifests when attackers craft maliciously nested markup structures that cause the ASP.NET runtime to perform excessive processing during view state validation. This occurs because the framework must recursively parse and validate the deeply nested elements, leading to exponential CPU consumption as the system attempts to process increasingly complex data structures. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption issue, specifically related to improper handling of input data that leads to excessive resource utilization.
From an operational impact perspective, this vulnerability enables remote attackers to execute denial of service attacks against ASP.NET applications by consuming significant CPU cycles on the web server. The attack is particularly effective because it requires minimal privileges and can be executed through normal web traffic without requiring authentication or specialized tools. The system becomes unresponsive to legitimate requests as the CPU resources are consumed by the malicious view state processing, effectively rendering the application unavailable to genuine users. This type of attack aligns with ATT&CK technique T1499.004 for Network Denial of Service, where adversaries leverage application-level vulnerabilities to exhaust system resources.
The mitigation strategies for this vulnerability include implementing cryptographic signing of view state data through the use of the ViewStateEncryptionMode property in ASP.NET applications, which ensures that view state data cannot be modified without detection. Organizations should also implement proper input validation and sanitization mechanisms to prevent the processing of malformed view state data. Additionally, deploying application-level firewalls or intrusion detection systems that can identify and block suspicious view state patterns can provide an additional layer of protection. The recommended approach involves configuring the web.config file to enable view state encryption and implementing proper resource monitoring to detect unusual CPU consumption patterns that may indicate exploitation attempts.