The IcedTea-Web project provides a Java web browser plug-in and an implementation of Java Web Start, which is based on the Netx project. It also contains a configuration tool for managing deployment settings for the plug-in and Web Start implementations.
It was discovered that the IcedTea-Web plug-in incorrectly used the same class loader instance for applets with the same value of the codebase attribute, even when they originated from different domains. A malicious applet could use this flaw to gain information about and possibly manipulate applets from different domains currently running in the browser. (CVE-2013-1926)
The IcedTea-Web plug-in did not properly check the format of the downloaded Java Archive (JAR) files. This could cause the plug-in to execute code hidden in a file in a different format, possibly allowing attackers to execute code in the context of web sites that allow uploads of specific file types, known as a GIFAR attack. (CVE-2013-1927)
The CVE-2013-1926 issue was discovered by Jiri Vanek of the Red Hat OpenJDK Team, and CVE-2013-1927 was discovered by the Red Hat Security Response Team.
This erratum also upgrades IcedTea-Web to version 1.2.3. Refer to the NEWS file, linked to in the References, for further information.
All IcedTea-Web users should upgrade to these updated packages, which resolve these issues. Web browsers using the IcedTea-Web browser plug-in must be restarted for this update to take effect.