CVE-2013-3171 in .NET Framework
Summary
by MITRE
The serialization functionality in Microsoft .NET Framework 2.0 SP2, 3.5, 3.5 SP1, 3.5.1, 4, and 4.5 does not properly check the permissions of delegate objects, which allows remote attackers to execute arbitrary code via (1) a crafted XAML browser application (XBAP) or (2) a crafted .NET Framework application that leverages a partial-trust relationship, aka "Delegate Serialization Vulnerability."
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 05/18/2021
The CVE-2013-3171 vulnerability represents a critical security flaw in Microsoft .NET Framework versions 2.0 SP2 through 4.5 that fundamentally undermines the security model designed to protect applications from malicious code execution. This vulnerability specifically targets the serialization functionality within the framework, which is responsible for converting objects into formats suitable for storage or transmission. The flaw occurs when the framework fails to properly validate permissions associated with delegate objects during the serialization process, creating a pathway for attackers to bypass security restrictions that should normally prevent code execution in restricted environments.
The technical nature of this vulnerability stems from the improper handling of delegate serialization in partial-trust environments where applications operate with limited permissions. When a .NET application runs in partial-trust mode, the runtime enforces strict security boundaries to prevent potentially malicious operations. However, the delegate serialization mechanism fails to adequately validate the permissions of delegate objects, allowing attackers to craft specially designed XAML browser applications or .NET applications that can exploit this weakness. The vulnerability manifests when an attacker constructs a malicious delegate object that, upon serialization and deserialization, can execute arbitrary code with elevated privileges that would normally be restricted in a partial-trust context.
The operational impact of CVE-2013-3171 is severe and multifaceted, as it affects a broad range of Microsoft .NET Framework versions that were widely deployed across enterprise environments and web applications. Attackers can leverage this vulnerability through two primary vectors: XAML browser applications that run in restricted trust zones and regular .NET applications that take advantage of partial-trust relationships. The attack surface is particularly concerning because XAML browser applications are commonly used for rich internet applications and can be easily delivered through web browsers, making them an attractive target for remote exploitation. Successful exploitation allows attackers to execute arbitrary code on affected systems, potentially leading to complete system compromise, data theft, or further network infiltration.
Mitigation strategies for CVE-2013-3171 require immediate attention and comprehensive implementation across affected environments. Microsoft released security updates that address the serialization flaw by strengthening the validation of delegate permissions during serialization processes. Organizations should prioritize applying these patches as soon as possible, particularly in environments where .NET Framework applications operate in partial-trust scenarios. Additional defensive measures include implementing network segmentation to limit exposure of affected systems, disabling unnecessary .NET Framework features, and monitoring for suspicious application behavior that might indicate exploitation attempts. From a compliance perspective, this vulnerability aligns with CWE-242, which addresses the weakness of using dangerous functions, and maps to ATT&CK technique T1059.001 for command and scripting interpreter usage, as exploitation typically involves executing malicious code within the .NET framework's execution environment. Organizations should also consider implementing application whitelisting policies and restricting the execution of XAML browser applications in environments where they are not strictly required.