CVE-2013-1336 in .NET Framework
Summary
by MITRE
The Common Language Runtime (CLR) in Microsoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4, and 4.5 does not properly check signatures, which allows remote attackers to make undetected changes to signed XML documents via unspecified vectors that preserve signature validity, aka "XML Digital Signature Spoofing Vulnerability."
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Analysis
by VulDB Data Team • 05/11/2021
The CVE-2013-1336 vulnerability represents a critical weakness in the Microsoft .NET Framework's handling of XML digital signatures, specifically within the Common Language Runtime component. This flaw affects multiple versions of the framework including 2.0 SP2, 3.5, 3.5.1, 4, and 4.5, making it a widespread concern across many enterprise environments. The vulnerability stems from insufficient validation mechanisms that should have prevented unauthorized modifications to signed XML documents while maintaining the appearance of validity.
The technical nature of this vulnerability lies in the CLR's failure to properly verify digital signatures during the processing of XML documents. When XML signatures are created, they are designed to ensure document integrity and authenticity by using cryptographic mechanisms to detect any alterations. However, this flaw allows attackers to manipulate XML content in such a way that the signature validation process continues to pass, even though the underlying document has been modified. The vulnerability operates through unspecified vectors that preserve the signature's validity while enabling content tampering.
This vulnerability directly impacts the security posture of systems relying on XML digital signatures for authentication and integrity verification. Attackers can exploit this weakness to inject malicious content into signed documents without detection, potentially leading to unauthorized access, data manipulation, or privilege escalation. The implications are particularly severe in enterprise environments where signed XML documents are used for authentication tokens, configuration files, or secure communications between systems. The vulnerability essentially undermines the fundamental security guarantee that digital signatures provide, allowing attackers to bypass signature validation entirely.
From a cybersecurity perspective, this vulnerability aligns with CWE-347, which addresses improper verification of cryptographic signatures, and maps to ATT&CK technique T1553.002 for valid accounts and T1070.004 for file and directory permissions modifications. Organizations using affected .NET Framework versions face significant risk as attackers can exploit this weakness to perform man-in-the-middle attacks, modify critical configuration files, or inject malicious code into trusted applications. The vulnerability's remote exploitation capability means that attackers do not need physical access to systems, making it particularly dangerous in networked environments.
Mitigation strategies should focus on immediate patching of affected .NET Framework versions, implementation of additional validation layers beyond the built-in signature checking, and monitoring for unauthorized XML document modifications. Organizations should also consider implementing network segmentation to limit the potential impact of exploitation, deploying intrusion detection systems to monitor for suspicious XML processing activities, and establishing robust change management procedures for XML-based configurations. Additionally, security teams should review existing XML signature validation processes and implement multi-factor verification mechanisms to compensate for the weakened signature integrity checks. The vulnerability highlights the critical importance of maintaining up-to-date security patches and the necessity of comprehensive security testing for cryptographic implementations.