CVE-2020-3994 in vCenter Server Appliance
Summary
by MITRE • 10/21/2020
VMware vCenter Server (6.7 before 6.7u3, 6.6 before 6.5u3k) contains a session hijack vulnerability in the vCenter Server Appliance Management Interface update function due to a lack of certificate validation. A malicious actor with network positioning between vCenter Server and an update repository may be able to perform a session hijack when the vCenter Server Appliance Management Interface is used to download vCenter updates.
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Analysis
by VulDB Data Team • 11/22/2020
The vulnerability identified as CVE-2020-3994 represents a critical session hijack flaw within VMware vCenter Server appliance management interfaces. This security weakness specifically affects versions 6.7 before 6.7u3 and 6.6 before 6.5u3k, creating a pathway for attackers to compromise the integrity of update processes through man-in-the-middle attacks. The vulnerability stems from insufficient certificate validation mechanisms during the update download process, which allows malicious actors positioned within the network to intercept and manipulate update communications. This flaw directly impacts the security posture of virtualized environments by undermining the trust model that should exist between the vCenter Server appliance and its update repositories.
The technical implementation of this vulnerability occurs within the vCenter Server Appliance Management Interface, where the update function fails to properly validate SSL/TLS certificates presented by update repositories. This certificate validation failure creates an opportunity for attackers to present fake certificates that appear legitimate to the vCenter Server appliance, enabling them to intercept update downloads and potentially inject malicious payloads. The flaw operates at the transport layer security validation step, where proper certificate chain verification and hostname matching should occur but do not. According to CWE classification, this represents a weakness in the validation of cryptographic certificates, specifically CWE-295 which addresses improper certificate validation. The vulnerability aligns with ATT&CK technique T1071.004 for application layer protocol: DNS, as it exploits network communication channels that are typically assumed to be secure.
The operational impact of this vulnerability extends beyond simple session hijacking to encompass potential compromise of the entire virtual infrastructure. When attackers successfully hijack update sessions, they can introduce malicious code into the vCenter Server environment, potentially gaining elevated privileges and persistent access to the management interface. The vulnerability affects the integrity of the update process, which is critical for maintaining security patches and system stability. Organizations running affected vCenter Server versions face significant risk of unauthorized modifications to their virtualization infrastructure, potentially leading to complete compromise of the vCenter Server management plane. The attack vector requires only network positioning between the vCenter Server and update repositories, making it particularly dangerous as it can be executed from within the organization's own network infrastructure. This vulnerability undermines the principle of least privilege and trust within the vCenter Server ecosystem, as it allows attackers to manipulate critical system updates that should be trusted and verified. The remediation process requires immediate patching of affected vCenter Server versions to implement proper certificate validation mechanisms and restore the security guarantees of the update process.
Organizations should implement immediate network segmentation to isolate vCenter Server appliances from untrusted network segments and establish secure update repositories with proper certificate management. The vulnerability demonstrates the critical importance of maintaining proper certificate validation in all network communications, particularly for management interfaces that handle sensitive system updates. Security teams must ensure that all vCenter Server environments are updated to patched versions that address this certificate validation weakness and implement monitoring for suspicious update activities. The vulnerability also highlights the need for comprehensive network security controls including intrusion detection systems and proper certificate pinning mechanisms to prevent similar attacks against other management interfaces.