CVE-2019-0545 in .NET Framework
Summary
by MITRE
An information disclosure vulnerability exists in .NET Framework and .NET Core which allows bypassing Cross-origin Resource Sharing (CORS) configurations, aka ".NET Framework Information Disclosure Vulnerability." This affects Microsoft .NET Framework 2.0, Microsoft .NET Framework 3.0, Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2, Microsoft .NET Framework 4.5.2, Microsoft .NET Framework 4.6, Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2, Microsoft .NET Framework 4.7/4.7.1/4.7.2, .NET Core 2.1, Microsoft .NET Framework 4.7.1/4.7.2, Microsoft .NET Framework 3.5, Microsoft .NET Framework 3.5.1, Microsoft .NET Framework 4.6/4.6.1/4.6.2, .NET Core 2.2, Microsoft .NET Framework 4.7.2.
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Analysis
by VulDB Data Team • 06/23/2023
The CVE-2019-0545 vulnerability represents a critical information disclosure flaw within Microsoft's .NET Framework and .NET Core implementations that fundamentally undermines cross-origin resource sharing security mechanisms. This vulnerability enables attackers to bypass CORS configurations that are designed to prevent unauthorized cross-domain requests, creating a significant security gap in web applications that rely on these frameworks for their backend services. The flaw specifically affects multiple versions of both the .NET Framework and .NET Core, spanning from version 2.0 through the latest 4.7.2 releases, as well as .NET Core 2.1 and 2.2, indicating a widespread impact across Microsoft's managed code execution environments.
The technical root cause of this vulnerability lies in how the .NET Framework and .NET Core handle CORS preflight requests and response headers, particularly when processing certain HTTP headers that should be restricted or filtered. Attackers can exploit this weakness by crafting malicious requests that manipulate the CORS validation process, allowing them to access resources that would normally be restricted based on origin policies. The vulnerability essentially allows unauthorized domains to access sensitive data that should be protected by CORS policies, potentially exposing application internals, user information, or system configuration details. This flaw operates at the HTTP protocol level within the framework's request processing pipeline, where the CORS validation logic fails to properly enforce security boundaries.
From an operational impact perspective, this vulnerability creates serious risks for organizations deploying applications built on affected .NET versions, as it can lead to unauthorized data access and potential information leakage. The attack surface is particularly concerning given that .NET Framework and .NET Core are widely used across enterprise environments, web applications, and cloud services. Security researchers have noted that the vulnerability can be exploited in conjunction with other techniques to escalate privileges or gain deeper system access, making it particularly dangerous in environments where sensitive data is processed. The information disclosure could range from application-specific data to system-level details that could aid in further exploitation attempts, aligning with ATT&CK technique T1213 for data exploitation and CWE-200 for information exposure.
Organizations affected by CVE-2019-0545 should immediately implement mitigation strategies including applying the relevant Microsoft security patches, reviewing and strengthening CORS configurations, and monitoring for suspicious cross-origin requests. The vulnerability demonstrates the importance of proper input validation and header handling in web frameworks, as outlined in CWE categories related to improper input validation and security misconfiguration. Security teams should also consider implementing additional network-level controls and monitoring for unusual CORS behavior, as the vulnerability can be difficult to detect through traditional security scanning methods. Microsoft has provided specific guidance for affected versions, emphasizing the need for comprehensive testing after applying patches to ensure no regression in application functionality occurs. The incident highlights the critical nature of maintaining up-to-date security patches across all components of the software stack, particularly those handling sensitive data access and cross-domain communications.