CVE-2017-4949 in Workstation
Summary
by MITRE
VMware Workstation and Fusion contain a use-after-free vulnerability in VMware NAT service when IPv6 mode is enabled. This issue may allow a guest to execute code on the host. Note: IPv6 mode for VMNAT is not enabled by default.
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Analysis
by VulDB Data Team • 01/29/2021
The vulnerability identified as CVE-2017-4949 represents a critical use-after-free flaw within VMware Workstation and Fusion products that specifically affects the VMware NAT service when IPv6 mode is enabled. This issue stems from improper memory management within the network address translation component that handles IPv6 traffic, creating a scenario where freed memory locations can be accessed and potentially manipulated by malicious actors. The vulnerability exists in the network virtualization layer that facilitates communication between virtual machines and the host system, making it particularly dangerous as it bridges the gap between guest and host environments. The flaw manifests when the NAT service processes IPv6 packets, leading to memory corruption that can be exploited to gain unauthorized access to the underlying host system.
The technical exploitation of this vulnerability requires a guest operating system to be compromised or controlled by an attacker who can then leverage the use-after-free condition to execute arbitrary code with elevated privileges on the host system. This represents a privilege escalation vulnerability that allows code execution at the host level, potentially enabling attackers to access sensitive data, install malware, or compromise the entire host environment. The vulnerability is classified under CWE-416 as a Use-After-Free condition, which occurs when a program continues to reference memory after it has been freed, creating opportunities for memory corruption attacks. The exploitation process typically involves crafting specific IPv6 network traffic that triggers the memory corruption, followed by a code execution payload that leverages the corrupted memory state to gain control over the host system.
The operational impact of CVE-2017-4949 extends beyond simple privilege escalation as it fundamentally undermines the security isolation between virtual machines and the host system. This vulnerability enables attackers to bypass the security boundaries that virtualization platforms are designed to maintain, potentially allowing for complete host compromise and data exfiltration. Organizations running VMware Workstation or Fusion with IPv6 mode enabled are particularly at risk, as the vulnerability requires only a compromised guest system to be exploited. The default disablement of IPv6 mode in VMNAT provides a mitigation path, but many environments may have this feature enabled for legitimate network connectivity reasons, creating a significant attack surface. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, as it provides a pathway for attackers to execute commands with elevated privileges.
Mitigation strategies for CVE-2017-4949 primarily focus on disabling IPv6 mode in VMware NAT when it is not required for network operations, which effectively neutralizes the vulnerability without impacting legitimate use cases. VMware released patches and updates to address this specific flaw, and organizations should ensure all systems are running patched versions of the affected software. Network segmentation and monitoring can help detect potential exploitation attempts, particularly around unusual IPv6 traffic patterns that might indicate an attack. Security administrators should also implement principle of least privilege configurations and ensure that virtual machines have minimal necessary network access permissions. The vulnerability demonstrates the critical importance of secure memory management in virtualization components and highlights the need for thorough security testing of network services within virtualized environments. Organizations should conduct regular vulnerability assessments to identify and remediate similar issues in their virtualization infrastructure, particularly focusing on network services that handle external traffic and maintain elevated privileges.