CVE-1999-0142 in Navigator
Summary
by MITRE
The Java Applet Security Manager implementation in Netscape Navigator 2.0 and Java Developer's Kit 1.0 allows an applet to connect to arbitrary hosts.
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Analysis
by VulDB Data Team • 04/16/2026
The vulnerability described in CVE-1999-0142 represents a critical security flaw in the Java applet security model implementation within Netscape Navigator 2.0 and the Java Developer's Kit 1.0 environments. This issue fundamentally undermines the sandbox security model that Java was designed to enforce, creating a significant pathway for malicious code execution. The security manager's implementation failed to properly restrict network connectivity permissions for applets, allowing untrusted code to establish connections to any host on the network without proper authorization. This weakness directly violates the core principle of Java's security architecture where applets should be confined to a restricted execution environment that prevents them from accessing system resources or network endpoints beyond their designated scope.
The technical flaw manifests in the inadequate enforcement of security policies within the Java Virtual Machine's security manager component. When a Java applet attempts to establish a network connection, the security manager should verify that the operation is permitted based on the applet's origin and the security policy configuration. However, in the affected versions, this verification mechanism was completely bypassed, allowing any applet to connect to arbitrary hosts regardless of its security context or the user's security preferences. This flaw operates at the level of the security policy enforcement layer, where the security manager fails to properly validate network connection requests against the established security boundaries. The vulnerability specifically affects the network permission checks that should normally prevent applets from making outbound connections to hosts outside their originating domain, effectively eliminating the network isolation that is fundamental to Java's security model.
The operational impact of this vulnerability is severe and far-reaching, as it enables attackers to craft malicious applets that can exfiltrate data, establish command and control connections, or perform other malicious network activities without detection. An attacker could create an applet that connects to external servers to download additional malware, steal sensitive information from the victim's network, or use the compromised system as a pivot point for further attacks. The vulnerability essentially eliminates the network security boundary that Java applets are supposed to respect, allowing them to communicate with any host on the network, including internal systems that should be protected from external access. This creates a pathway for attackers to bypass network firewalls and security controls that rely on the assumption that applets cannot make arbitrary network connections, potentially leading to data breaches, system compromise, and unauthorized access to sensitive resources. The vulnerability affects a critical security component that is fundamental to the secure execution of untrusted code in web browsers, making it particularly dangerous in enterprise environments where network security is paramount.
Mitigation strategies for this vulnerability require immediate implementation of security patches and updates to the affected software versions. Organizations should upgrade to newer versions of Netscape Navigator and Java Developer's Kit that properly implement security manager functionality, ensuring that network connectivity restrictions are enforced correctly. The recommended approach includes deploying security updates from the software vendors that address the flawed security policy enforcement mechanism. Additionally, system administrators should consider implementing network-level controls such as firewall rules that restrict outbound connections from web browsers and application servers, creating additional layers of defense. Configuration management should enforce strict security policies that prevent applets from making network connections unless explicitly authorized through secure policy files. The vulnerability aligns with CWE-284 which addresses improper access control in software systems, and relates to ATT&CK technique T1059.007 for application layer protocol execution through web browsers. Organizations should also consider implementing network monitoring and intrusion detection systems to detect unauthorized network connections initiated by Java applets, providing visibility into potential exploitation attempts. Regular security assessments and penetration testing should be conducted to verify that security controls are properly enforced and that no other similar vulnerabilities exist in the Java runtime environment or related components.