CVE-2017-4938 in Workstation
Summary
by MITRE
VMware Workstation (12.x before 12.5.8) and Fusion (8.x before 8.5.9) contain a guest RPC NULL pointer dereference vulnerability. Successful exploitation of this issue may allow attackers with normal user privileges to crash their VMs.
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Analysis
by VulDB Data Team • 01/24/2021
The vulnerability identified as CVE-2017-4938 represents a critical NULL pointer dereference flaw within VMware Workstation and Fusion virtualization platforms. This issue affects VMware Workstation versions 12.x prior to 12.5.8 and Fusion versions 8.x prior to 8.5.9, creating a significant security risk for users operating these virtualization environments. The vulnerability stems from improper input validation within the guest RPC (Remote Procedure Call) implementation, where the system fails to properly check for NULL references before attempting to dereference pointers. This flaw exists in the communication layer between host and guest operating systems, specifically when processing RPC requests from guest virtual machines. The vulnerability is classified under CWE-476 as a NULL Pointer Dereference, which is a common class of software defects that can lead to system instability and potential privilege escalation scenarios.
The operational impact of this vulnerability extends beyond simple system crashes, as it can be exploited by attackers with normal user privileges to cause denial of service conditions within virtualized environments. When a guest VM attempts to execute a malformed RPC request, the host system's RPC handler fails to validate pointer references, resulting in a segmentation fault or system crash. This vulnerability particularly affects multi-user environments where guest VMs might be running untrusted code or where privilege escalation attacks could be attempted. The flaw demonstrates a fundamental weakness in VMware's virtualization layer security model, as it allows a low-privilege attacker within a guest operating system to disrupt the functionality of the entire virtual machine environment. This type of vulnerability aligns with ATT&CK technique T1499.001 for Network Denial of Service and represents a classic example of how virtualization layer flaws can be exploited to compromise system availability.
Mitigation strategies for CVE-2017-4938 primarily focus on immediate patch application, as VMware released updates to address this specific vulnerability in versions 12.5.8 and 8.5.9 respectively. Organizations should implement comprehensive patch management procedures to ensure all virtualization environments are updated promptly. Additionally, network segmentation and access controls should be enforced to limit guest VM privileges and reduce the attack surface. Security monitoring should be enhanced to detect unusual RPC traffic patterns that might indicate exploitation attempts. The vulnerability highlights the importance of input validation and proper error handling in virtualization software, as similar flaws could exist in other components of the virtualization stack. Organizations should also consider implementing virtual machine isolation measures and regularly auditing their virtualization environments for similar security weaknesses. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date virtualization software and following security best practices in multi-tenant virtualized environments. The flaw demonstrates how seemingly minor implementation issues in virtualization layers can have significant operational impacts, particularly in enterprise environments where virtualization is extensively utilized for various business functions.