Java Runtime Environment (JRE) Bytecode Verifier allows remote attackers to escape the Java sandbox and execute commands via an applet containing an illegal cast operation, as seen in (1) Microsoft VM build 3802 and earlier as used in Internet Explorer 4.x and 5.x, (2) Netscape 6.2.1 and earlier, and possibly other implementations that use vulnerable versions of SDK or JDK, aka a variant of the "Virtual Machine Verifier" vulnerability.
Vulnerability in Java Runtime Environment (JRE) allows remote malicious web sites to hijack or sniff a web client's sessions, when an HTTP proxy is being used, via a Java applet that redirects the session to another server, as seen in (1) Netscape 6.0 through 6.1 and 4.79 and earlier, (2) Microsoft VM build 3802 and earlier as used in Internet Explorer 4.x and 5.x, and possibly other implementations that use vulnerable versions of SDK or JDK.
Java Plugin 1.4 for JRE 1.3 executes signed applets even if the certificate is expired, which could allow remote attackers to conduct unauthorized activities via an applet that has been signed by an expired certificate.