Oracle addressed 40 security issues in Java and enabled online certificate revocation checking by default in its scheduled critical patch update for Java on Tuesday.
Thirty-four vulnerabilities patched in the newly released Java 7 Update 25 (Java 7u25) version affect only client deployments of Java. Another four affect both client and server deployments, one affects the Java installer and one the Javadoc tool that's used to create HTML documentation files.
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Many of the client-only vulnerabilities received the maximum score on the vulnerability severity scale used by Oracle. These flaws can be exploited by attackers to take control of computers by hosting malicious Java applets -- Java Web applications -- on remote servers and tricking users to load them in their browsers.
The large number of Web-based attacks that targeted Java users this year by exploiting vulnerabilities in the Java browser plug-in prompted concern about the security worthiness of the Java platform among home users and in enterprise environments, where Java is also frequently used on servers.
In order to clearly differentiate between the security risks to Java client and server deployments, Oracle started shipping a separate Server JRE (Java Runtime Environment) package in April that doesn't include the browser plug-in.
The Javadoc issue could affect users who visit HTML pages generated with the tool that are hosted on Web servers.
"Some HTML pages that were created by any 1.5 or later versions of the Javadoc tool are vulnerable to frame injection," said Eric Maurice, Oracle's director of software assurance, in a blog post Tuesday. "If exploited, this vulnerability can result in granting a malicious attacker the ability to inject frames into a vulnerable web page, thus allowing the attacker to direct unsuspecting users to malicious web pages through their web browsers."
Java 7u25 includes a patched version of the Javadoc tool that no longer generates vulnerable Web pages. In addition, Oracle released a separate tool called the Java API Documentation Updater Tool, that can be used to fix previously generated and vulnerable pages.
The new update also makes some other security-related changes, including enabling the certificate revocation checking feature by default.
As part of its efforts to fight Java exploits, Oracle changed Java's default behavior earlier this year to prevent the execution of unsigned applets without user interaction, therefore encouraging developers to digitally sign their Java Web applications with valid certificates.
However, in order for this to work properly as a defense mechanism, Java needs to be able to check in real time if the certificates used to sign applets have been revoked by their issuing certificate authorities (CAs). Otherwise, an attacker could sign a malicious applet with a stolen certificate and there would be no way for Java to detect that, even if the CA later revoked the certificate for abuse.