CVE-2020-0756 in Windows
Summary
by MITRE
An information disclosure vulnerability exists in the Cryptography Next Generation (CNG) service when it fails to properly handle objects in memory.To exploit this vulnerability, an attacker would have to log on to an affected system and run a specially crafted application.The security update addresses the vulnerability by correcting how the service handles objects in memory., aka 'Windows Key Isolation Service Information Disclosure Vulnerability'. This CVE ID is unique from CVE-2020-0675, CVE-2020-0676, CVE-2020-0677, CVE-2020-0748, CVE-2020-0755.
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Analysis
by VulDB Data Team • 03/30/2024
The vulnerability described in CVE-2020-0756 represents a critical information disclosure flaw within Microsoft's Cryptography Next Generation (CNG) service, specifically affecting the Windows Key Isolation Service component. This issue arises from improper memory handling mechanisms within the cryptographic service that governs how encryption keys and sensitive cryptographic objects are managed in system memory. The vulnerability is particularly concerning because it requires only local user authentication to exploit, making it accessible to attackers who have already gained initial system access through other means such as phishing attacks or credential theft. The flaw manifests when the CNG service processes cryptographic objects in memory without adequate safeguards, potentially exposing sensitive key material or cryptographic data that should remain isolated and protected.
The technical root cause of this vulnerability lies in the insufficient validation and handling of memory objects within the Windows Key Isolation Service, which is designed to protect cryptographic keys from unauthorized access and manipulation. When the service fails to properly manage memory allocation and deallocation for cryptographic objects, it creates opportunities for information leakage that could expose sensitive cryptographic material. This type of vulnerability falls under the CWE-200 category of "Information Exposure" and specifically relates to improper handling of sensitive data in memory. The flaw enables an attacker with local system access to potentially extract cryptographic keys, certificates, or other sensitive information that should be protected by the key isolation service. The attack vector requires the adversary to be authenticated to the system, but once achieved, the vulnerability allows for the extraction of information that could compromise the entire cryptographic infrastructure.
From an operational impact perspective, this vulnerability significantly weakens the security posture of affected Windows systems by undermining the fundamental security assumptions of the key isolation service. The information disclosure could lead to the compromise of encrypted data, facilitate man-in-the-middle attacks, or enable attackers to impersonate legitimate users or services. The vulnerability affects systems running Windows 10 versions 1903 and 1909, as well as Windows Server 2019 and Windows Server 2016, making it particularly impactful for enterprise environments where these operating systems are prevalent. The security update addresses this issue by implementing proper memory handling procedures that ensure cryptographic objects are correctly isolated and protected during processing. This remediation aligns with the ATT&CK framework's technique T1552.001 for "Unsecured Credentials" and T1003.002 for "OS Credential Dumping" as it directly addresses weaknesses in how cryptographic credentials are handled in memory.
Organizations should prioritize patching affected systems immediately as this vulnerability could be leveraged in conjunction with other attack vectors to escalate privileges or compromise additional system components. The vulnerability's impact is amplified when combined with other local privilege escalation flaws, as demonstrated in various threat actor methodologies that combine multiple vulnerabilities to achieve persistent access. Security teams should monitor for signs of exploitation attempts and implement additional controls such as memory inspection tools and monitoring for unauthorized access to cryptographic objects. The vulnerability serves as a reminder of the critical importance of proper memory management in security-critical services and highlights the need for comprehensive security testing of cryptographic implementations. Organizations should also consider implementing additional layers of protection such as hardware security modules or trusted platform modules to provide additional isolation for sensitive cryptographic operations beyond the software-based key isolation service.