CVE-2000-0327 in Virtual Machine
Summary
by MITRE
Microsoft Virtual Machine (VM) allows remote attackers to escape the Java sandbox and execute commands via an applet containing an illegal cast operation, aka the "Virtual Machine Verifier" vulnerability.
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Analysis
by VulDB Data Team • 04/19/2026
The CVE-2000-0327 vulnerability represents a critical security flaw in Microsoft's Virtual Machine implementation that fundamentally compromised the Java sandbox security model. This vulnerability specifically targeted the Java bytecode verification process within Microsoft's VM, which was designed to prevent malicious code from executing unauthorized operations. The flaw allowed attackers to bypass the security restrictions that normally isolate applets from the underlying operating system, creating a pathway for arbitrary code execution.
The technical root cause of this vulnerability stems from an insufficient verification mechanism within the Microsoft Virtual Machine's bytecode verifier. When processing Java applets, the VM failed to properly validate certain cast operations that should have been rejected during the verification phase. This weakness occurred because the verifier did not adequately check the type safety of specific bytecode instructions, particularly those involving illegal cast operations that could be manipulated to execute privileged operations. The vulnerability falls under the CWE-119 category of "Improper Restriction of Operations within the Bounds of a Memory Buffer" and more specifically aligns with CWE-252, "Unchecked Return Value," as the verification process did not properly validate return values from critical type checking operations.
The operational impact of this vulnerability was severe and far-reaching, as it enabled remote attackers to completely escape the confines of the Java sandbox environment. Attackers could craft malicious applets that, when executed by a vulnerable Microsoft VM, would allow them to perform system-level operations including file manipulation, network communication, and arbitrary command execution. This represented a complete breakdown of the security model that Java applets were designed to provide, as the sandbox protection mechanism was effectively neutralized. The vulnerability was particularly dangerous because it could be exploited through web browsers that included the Microsoft VM, making it accessible to a wide range of potential victims.
From an attack framework perspective, this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework, particularly in the execution and privilege escalation domains. The vulnerability enabled initial access through malicious applets delivered via web pages, followed by privilege escalation to system-level operations. The attack chain typically involved crafting a specially designed applet that would trigger the illegal cast operation, causing the VM to execute unauthorized code. This vulnerability also demonstrated the importance of proper input validation and the critical nature of bytecode verification in sandboxed environments, as highlighted in various cybersecurity best practices and standards.
Mitigation strategies for this vulnerability required immediate patching of affected Microsoft Virtual Machine implementations, as well as the discontinuation of use for vulnerable browser configurations. Organizations needed to ensure that their systems were updated with the appropriate security patches from Microsoft, and in many cases, the complete removal of the Microsoft VM from web browsers was necessary. The vulnerability underscored the importance of maintaining up-to-date security implementations and the critical need for robust verification mechanisms in sandboxed environments. Additionally, network administrators should have implemented monitoring for suspicious applet execution patterns and ensured that web content was properly validated before execution. This vulnerability ultimately led to increased awareness of the security implications of sandboxed environments and the necessity of comprehensive verification processes in virtual machine implementations.