CVE-2019-5535 in Workstation
Summary
by MITRE
VMware Workstation and Fusion contain a network denial-of-service vulnerability due to improper handling of certain IPv6 packets. VMware has evaluated the severity of this issue to be in the Moderate severity range with a maximum CVSSv3 base score of 4.7.
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Analysis
by VulDB Data Team • 10/01/2020
The vulnerability identified as CVE-2019-5535 represents a network denial-of-service weakness affecting VMware Workstation and Fusion virtualization platforms. This issue stems from the improper handling of specific IPv6 packets within the virtual network stack implementation. The flaw manifests when the virtualized environment processes malformed or specially crafted IPv6 packets that trigger unexpected behavior in the network processing components. The vulnerability impacts both VMware Workstation 15.x versions prior to 15.5.1 and VMware Fusion 11.x versions prior to 11.5.1, creating a significant operational risk for users running these virtualization products. The affected systems experience network disruption when encountering these specific packet structures, leading to complete network service unavailability within the virtual environment.
The technical root cause of this vulnerability lies in the insufficient validation and processing logic within the IPv6 packet handling mechanisms of the virtual network adapters. When the virtual machine processes IPv6 packets containing malformed header structures or unexpected field values, the network driver fails to properly sanitize the input before processing. This inadequate input validation creates a condition where the processing routine can be forced into an unexpected state, ultimately leading to a denial-of-service scenario. The vulnerability specifically targets the IPv6 fragmentation handling routines where the system fails to properly validate packet boundaries and header integrity. This weakness allows an attacker positioned on the network to send carefully crafted IPv6 packets that cause the virtual network interface to become unresponsive, effectively cutting off all network connectivity for the affected virtual machine.
From an operational perspective, this vulnerability presents a moderate severity risk that can significantly impact virtualized environments where network connectivity is critical for system functionality. The denial-of-service condition affects the entire virtual network interface, rendering the virtual machine incapable of communicating with external networks or other virtual machines within the same environment. This disruption can cascade through dependent services and applications that rely on network connectivity within the virtualized infrastructure. Organizations using VMware Workstation or Fusion for development, testing, or production environments face potential service interruptions that could impact business operations. The vulnerability is particularly concerning in environments where virtual machines are configured with automatic network management or where network availability is critical for application performance. The CVSSv3 base score of 4.7 indicates that while the impact is not severe, the vulnerability can still cause meaningful disruption to network services.
The vulnerability aligns with CWE-129, which addresses issues related to improper validation of input boundaries, and CWE-248, which covers unexpected exceptions in the network processing components. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 which covers network denial-of-service attacks, and T1071.004 which involves application layer protocol usage for network communication. Organizations should implement immediate mitigations including applying the vendor patches released by VMware, which address the IPv6 packet handling logic to properly validate incoming packets before processing. Network segmentation and firewall rules can provide additional protection by limiting access to vulnerable virtual machines and monitoring for suspicious IPv6 packet patterns. Regular vulnerability assessments should include checking for outdated VMware installations and ensuring all virtualization components are updated to the latest security patches. The recommended remediation approach involves upgrading to VMware Workstation 15.5.1 or later versions, and VMware Fusion 11.5.1 or later versions, which contain the necessary fixes to prevent the improper IPv6 packet handling that leads to the denial-of-service condition.