CVE-2020-3976 in ESXi
Summary
by MITRE
VMware ESXi and vCenter Server contain a partial denial of service vulnerability in their respective authentication services. VMware has evaluated the severity of this issue to be in the Moderate severity range with a maximum CVSSv3 base score of 5.3.
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Analysis
by VulDB Data Team • 08/22/2020
The vulnerability identified as CVE-2020-3976 affects VMware ESXi and vCenter Server authentication services, representing a partial denial of service condition that impacts the availability of critical system functions. This issue resides within the authentication mechanisms of VMware's virtualization platform, specifically targeting the credential validation processes that govern access to these enterprise systems. The vulnerability was assessed by VMware with a moderate severity rating and a CVSSv3 base score of 5.3, indicating a moderate risk to affected environments. The authentication service components are fundamental to the operation of VMware's infrastructure, making this vulnerability particularly concerning for organizations that rely heavily on virtualized environments for their computing needs.
The technical flaw manifests in the authentication service implementation where certain conditions can cause the system to enter a partial denial of service state during credential validation processes. This occurs when the authentication subsystem fails to properly handle specific authentication requests, leading to temporary unavailability of authentication services for legitimate users. The vulnerability does not completely disable the authentication system but rather creates a partial disruption that affects the ability to authenticate new connections or validate existing credentials. The underlying mechanism involves improper error handling within the authentication service code, where certain input patterns or authentication sequences trigger unexpected behavior that impacts service availability. This type of vulnerability falls under CWE-400, which addresses improper handling of resources, and specifically relates to the CWE-284 access control weaknesses that affect authentication systems.
The operational impact of CVE-2020-3976 extends beyond simple service disruption as it affects the core functionality of VMware's virtualization infrastructure. Organizations utilizing affected ESXi and vCenter Server versions may experience intermittent authentication failures that could disrupt administrative access to virtual machines, impact backup operations, and affect overall system management capabilities. The partial denial of service condition means that while some authentication requests may succeed, others will fail, creating an inconsistent and unreliable authentication environment. This instability can particularly affect automated systems that rely on consistent authentication services, potentially causing cascading failures in dependent services. The vulnerability also creates opportunities for attackers to exploit the authentication service instability, potentially leading to more severe impacts if combined with other attack vectors. From an ATT&CK framework perspective, this vulnerability aligns with T1110 credential access techniques that involve exploiting authentication system weaknesses to gain unauthorized access or disrupt legitimate access.
Mitigation strategies for CVE-2020-3976 primarily focus on applying VMware's official security patches and updates to affected systems. Organizations should prioritize patching both ESXi hosts and vCenter Server instances to address the authentication service vulnerabilities. Additionally, implementing network segmentation and access controls can help limit exposure by restricting direct access to authentication services from untrusted networks. Monitoring authentication logs for unusual patterns or repeated authentication failures can help detect exploitation attempts or identify systems that may be affected by the vulnerability. Security teams should also consider implementing additional authentication layers or multi-factor authentication mechanisms to reduce the impact of potential exploitation. Regular vulnerability assessments and penetration testing should be conducted to identify similar weaknesses in the authentication infrastructure. The remediation process should include thorough testing of patches in non-production environments before deployment to ensure compatibility with existing systems and prevent unintended service disruptions. Organizations should also maintain updated inventory records of all VMware products and versions to quickly identify and remediate affected systems across their infrastructure.