CVE-1999-0141 in Navigator
Summary
by MITRE
java bytecode verifier allows malicious applets to execute arbitrary commands as the user of the applet.
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Analysis
by VulDB Data Team • 04/03/2025
The vulnerability described in CVE-1999-0141 represents a critical security flaw in the java bytecode verification mechanism that existed in early versions of the java runtime environment. This weakness allowed malicious applets to bypass the security restrictions imposed by the java sandbox model, effectively enabling attackers to execute arbitrary commands on users' systems with the privileges of the logged-in user. The issue stemmed from insufficient validation of bytecode instructions during the verification process, creating a pathway for malicious code to circumvent the security boundaries designed to protect users from untrusted applet code.
The technical implementation of this vulnerability exploited the java bytecode verifier's failure to properly validate certain instruction sequences that could be used to construct malicious code patterns. When a java applet was loaded and executed, the bytecode verifier was responsible for ensuring that the applet's code adhered to java security restrictions and could not perform dangerous operations such as file system access, network connections to arbitrary hosts, or system command execution. However, the flaw allowed attackers to craft bytecode sequences that would pass verification checks while containing hidden malicious payloads that could execute system commands through java's reflection or native method invocation capabilities.
The operational impact of this vulnerability was severe and far-reaching, as it enabled attackers to compromise user systems through web browsers that supported java applets. Users could be exploited simply by visiting compromised websites or downloading malicious applets, making this a particularly dangerous vulnerability for widespread deployment. The attack vector typically involved social engineering tactics where users would be tricked into downloading and executing malicious applets, which would then leverage the verification flaw to execute commands on the victim's system. This could result in complete system compromise, data theft, or the installation of additional malware.
Organizations and individuals could mitigate this vulnerability through several approaches that aligned with established security practices and frameworks. The primary mitigation involved updating to patched versions of the java runtime environment where the bytecode verification process was corrected to properly validate all instruction sequences. Additionally, system administrators could implement browser security policies that disabled java applet execution entirely, particularly in environments where the risk was deemed unacceptable. From a compliance perspective, this vulnerability highlighted the importance of proper input validation and code verification processes, aligning with common weakness enumerations such as CWE-110 and CWE-111 which focus on inadequate verification of security controls and improper handling of potentially dangerous code sequences. The incident also demonstrated the critical need for robust sandboxing mechanisms and proper privilege separation, concepts that are fundamental to the ATT&CK framework's approach to defending against privilege escalation and code execution attacks. Organizations implementing security controls should have considered this vulnerability as part of broader application security testing and runtime protection strategies to prevent similar issues in the future.