CVE-2015-1672 in .NET Framework
Summary
by MITRE
Microsoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4, 4.5, 4.5.1, and 4.5.2 allows remote attackers to cause a denial of service (recursion and performance degradation) via crafted encrypted data in an XML document, aka ".NET XML Decryption Denial of Service Vulnerability."
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Analysis
by VulDB Data Team • 05/17/2022
The vulnerability identified as CVE-2015-1672 represents a critical denial of service weakness within Microsoft .NET Framework versions spanning from 2.0 SP2 through 4.5.2. This flaw specifically targets the XML decryption functionality and enables remote attackers to exploit recursive processing behaviors that consume excessive system resources. The vulnerability stems from insufficient validation of encrypted XML data structures during the decryption process, creating conditions where malformed or specially crafted encrypted content can trigger infinite recursion patterns within the framework's processing logic.
The technical implementation of this vulnerability occurs when the .NET Framework attempts to decrypt XML documents containing maliciously constructed encrypted data. During the decryption operation, the framework's XML parser encounters recursive references within the encrypted content that are not properly bounded or validated. This allows attackers to construct XML documents with encrypted elements that reference themselves or create circular dependencies, leading to uncontrolled recursion within the decryption engine. The flaw manifests as a performance degradation that can escalate to complete system resource exhaustion, effectively rendering the affected system unavailable to legitimate users. This behavior aligns with CWE-674, which describes "Uncontrolled Recursion" as a weakness where a recursive process lacks proper termination conditions.
From an operational perspective, this vulnerability presents significant risk to systems running affected .NET Framework versions, particularly those handling XML-based communications or processing external data sources. Attackers can exploit this weakness by sending specially crafted XML documents containing encrypted data to any application that relies on .NET Framework's XML decryption capabilities. The impact extends beyond simple service disruption as the resource exhaustion can affect system stability, potentially causing applications to crash or become unresponsive. This vulnerability is particularly dangerous in web applications, enterprise systems, and services that process user-supplied XML data, as it can be exploited through common attack vectors such as file uploads, API endpoints, or web services that accept XML input.
The exploitation of CVE-2015-1672 follows patterns consistent with the attack technique described in the MITRE ATT&CK framework under the T1499 category for "Network Denial of Service" and T1210 for "Exploitation of Remote Services." The vulnerability can be leveraged in scenarios where attackers have access to systems that process XML data through .NET Framework components, making it particularly relevant for attack chains involving web application exploitation or service disruption campaigns. Organizations using affected .NET Framework versions should implement immediate mitigations including applying the relevant Microsoft security updates, implementing input validation controls, and monitoring for unusual resource consumption patterns that might indicate exploitation attempts. Additionally, network segmentation and application-level filtering of XML content can provide additional defense-in-depth measures to reduce the attack surface and limit the potential impact of successful exploitation attempts.