CVE-2016-7270 in .NET Framework
Summary
by MITRE
The Data Provider for SQL Server in Microsoft .NET Framework 4.6.2 mishandles a developer-supplied key, which allows remote attackers to bypass the Always Encrypted protection mechanism and obtain sensitive cleartext information by leveraging key guessability, aka ".NET Information Disclosure Vulnerability."
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Analysis
by VulDB Data Team • 10/08/2022
The vulnerability identified as CVE-2016-7270 represents a critical flaw in Microsoft .NET Framework 4.6.2 that undermines the security assurances provided by the Always Encrypted feature. This weakness specifically affects the Data Provider for SQL Server component, which is responsible for handling encrypted data operations within the framework. The vulnerability stems from improper handling of developer-supplied encryption keys, creating a pathway for malicious actors to bypass the intended protection mechanisms. The flaw exploits the predictability and guessability of certain key parameters, allowing attackers to recover cleartext information from encrypted data that should remain protected. This issue directly impacts organizations that rely on Always Encrypted for database security, as it fundamentally compromises the confidentiality guarantees that this feature is designed to provide.
The technical implementation of this vulnerability resides in how the .NET Framework processes encryption keys when developers provide custom key material for Always Encrypted operations. The framework fails to adequately validate or secure these developer-supplied keys, creating opportunities for attackers to exploit patterns or weaknesses in key generation or handling. According to CWE classification, this vulnerability maps to CWE-20: Improper Input Validation, as it involves inadequate validation of cryptographic key parameters. The flaw enables attackers to perform information disclosure attacks by leveraging predictable key structures, effectively breaking the encryption boundaries that should protect sensitive data. The vulnerability's impact is particularly severe because it operates at the data provider level, meaning that any application using Always Encrypted with custom keys could be susceptible to this attack vector. The attack requires remote access capabilities but does not necessarily require elevated privileges, making it accessible to a wide range of threat actors.
The operational consequences of CVE-2016-7270 extend far beyond simple data exposure, as it fundamentally undermines the trust model that organizations place in their database encryption solutions. Organizations implementing Always Encrypted may experience significant security breaches where sensitive information such as personal identification data, financial records, or proprietary business information becomes accessible to unauthorized parties. The vulnerability affects applications that use custom encryption keys rather than relying on the default system-managed keys, which represents a common practice among enterprise developers seeking greater control over their encryption policies. This flaw can lead to compliance violations under various regulatory frameworks including pci dss, hipaa, and gdpr, as organizations may inadvertently expose protected data. The attack vector is particularly concerning because it operates silently in the background, allowing attackers to extract cleartext data without triggering obvious security alerts. According to ATT&CK framework categorization, this vulnerability aligns with T1552.001: Unsecured Credentials and T1005: Data from Local System, as it involves unauthorized access to encrypted data through compromised key handling mechanisms.
Mitigation strategies for CVE-2016-7270 require immediate action from affected organizations to address the root cause of the vulnerability. Microsoft released patches and updates for the .NET Framework that resolve the key handling issues, and organizations must apply these updates promptly to protect their systems. The recommended approach involves upgrading to the latest .NET Framework version that includes the security fixes, along with implementing additional monitoring and detection capabilities to identify potential exploitation attempts. Security teams should conduct comprehensive audits of all applications that utilize Always Encrypted with custom keys to ensure proper implementation and key management practices. Organizations should also consider implementing additional layers of security such as network segmentation, intrusion detection systems, and regular security assessments to detect unauthorized access attempts. The vulnerability highlights the importance of proper cryptographic key management practices and demonstrates why organizations should avoid using predictable or easily guessable key materials in encryption implementations. Regular security training for developers on secure coding practices and encryption key management is essential to prevent similar issues in future implementations.