CVE-2006-3436 in ASP.NET
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Microsoft .NET Framework 2.0 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors involving "ASP.NET controls that set the AutoPostBack property to true".
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Analysis
by VulDB Data Team • 04/24/2026
The vulnerability identified as CVE-2006-3436 represents a critical cross-site scripting flaw within Microsoft .NET Framework 2.0 that specifically affects web applications utilizing ASP.NET controls with AutoPostBack functionality enabled. This weakness falls under the broader category of CWE-79 Improper Neutralization of Input During Web Page Generation, which is a fundamental web security principle that addresses the improper handling of user-supplied data in web applications. The vulnerability stems from insufficient sanitization of input data within the framework's control rendering mechanisms, creating a pathway for malicious actors to inject arbitrary script code into web pages that are subsequently executed by victim browsers. The specific context of this vulnerability involves ASP.NET server controls that automatically trigger postback events when user interactions occur, such as dropdown list selections or checkbox toggles, which creates an attack surface where user input can be improperly processed and reflected back to other users.
The technical exploitation of this vulnerability occurs when ASP.NET controls with AutoPostBack set to true process user input without adequate validation or encoding mechanisms. When a user interacts with such a control, the framework generates a postback request that includes the user-supplied data, which is then processed and potentially rendered back to other users without proper sanitization. This creates a classic XSS scenario where malicious script code can be injected through form fields, URL parameters, or other user-controllable inputs that are subsequently processed by the vulnerable controls. The vulnerability is particularly concerning because it affects core framework components rather than individual applications, meaning that any web application built on .NET Framework 2.0 that utilizes these specific controls is potentially at risk. The attack vector typically involves crafting malicious input that, when processed by the ASP.NET control system, gets embedded into the HTML output and executed in the context of other users' browsers, potentially leading to session hijacking, credential theft, or other malicious activities.
The operational impact of CVE-2006-3436 extends beyond simple script injection, as it can enable sophisticated attack chains that leverage the broader ATT&CK framework's T1531 Lateral Tool Transfer and T1059 Command and Scripting Interpreter techniques. An attacker who successfully exploits this vulnerability can potentially establish persistent access to user sessions, steal authentication tokens, redirect users to malicious sites, or even deploy additional malicious payloads through the compromised web application. The vulnerability affects not just the immediate execution environment but also the trust relationships within web applications, as the injected scripts can access cookies, local storage, and other browser resources that are normally protected. Organizations running .NET Framework 2.0 applications with AutoPostBack controls face significant risk of data breaches, service disruption, and potential regulatory compliance violations, particularly in environments where sensitive data processing occurs. The vulnerability's impact is amplified by the widespread adoption of the .NET Framework 2.0 platform, making it a prime target for automated exploitation tools and increasing the potential attack surface across numerous applications and organizations.
Mitigation strategies for this vulnerability require a multi-layered approach combining immediate patching with defensive programming practices. The most effective immediate solution involves applying Microsoft's security patches and updates that address the specific XSS handling in the .NET Framework 2.0 controls, which should be prioritized as critical security updates. Organizations should also implement comprehensive input validation and output encoding mechanisms at the application level, ensuring that all user-supplied data is properly sanitized before being processed by ASP.NET controls. This includes implementing proper HTML encoding for all dynamic content, utilizing the framework's built-in validation controls, and considering the use of Content Security Policy headers to limit script execution. Additionally, security developers should review their application code to identify and disable AutoPostBack functionality where it is not essential, as well as implement proper error handling and logging to detect potential exploitation attempts. The implementation of these mitigations aligns with security best practices outlined in the OWASP Top Ten and follows the principle of defense in depth, ensuring that even if one layer fails, other controls can prevent or detect the exploitation of the vulnerability.