Software Engineering Institute

Signed Java applets have the ability to perform actions outside of the traditional Java sandbox, including local filesystem access or the ability to execute native code. When a user encounters a signed Java applet in a web page, the JRE will provide a dialog asking the user if they wish to run the application. The default for this dialog is "Always trust content from this publisher." This means that once a signed Java applet is executed, all applets that are determined to be signed by that vendor will execute without requiring any user interaction. Please see the CERT Vulnerability Analysis Blog for more details.

Oracle Sun Java contains a critical flaw in the validation of Java applet signatures. This vulnerability can allow an attacker to modify the contents of a signed Java applet without breaking the signature. The Oracle Critical Patch Update lists the following versions as being affected:
Java SE:

• JDK and JRE 6 Update 18 and earlier for Windows, Solaris, and Linux
• JDK 5.0 Update 23 and earlier for Solaris
• SDK 1.4.2_25 and earlier for Solaris

• JDK and JRE 6 Update 18 and earlier for Windows, Solaris and Linux
• JDK and JRE 5.0 Update 23 and earlier for Windows, Solaris and Linux
• SDK and JRE 1.4.2_25 and earlier for Windows, Solaris and Linux

By convincing a user to execute a signed Java applet, e.g. by visiting a website, a remote, unauthenticated attacker may be able to execute arbitrary code on a vulnerable system.

Apply an updateThis issue has been addressed by the Java updates specified in the Oracle Java Critical Patch Update - March 2010 document.

Disable Java

This and other Java vulnerabilities can be mitigated by disabling Java support in your web browser. Details are available in the Securing Your Web Browser document.

Disable signed Java

Details for disabling signed Java are available in the CERT Vulnerability Analysis Blog entry Signed Java Applet Security: Worse than ActiveX?.