Over the past two days, two actively exploited 0day vulnerabilities got patched. Yesterday, Oracle addressed the 0day in Java, CVE-2013-0422, with an new update, Java 7u11. Today, Microsoft addressed the 0day in Internet Explorer 6-9, CVE-2012-4792, with MS13-008.
In addition to fixing the 0day vulnerability, the Java update changes the default security level setting from medium to high. This means that users will be prompted before running unsigned or self-signed Java applets or Java Web Start applications are run. With this update, silent exploitation will no longer be an option to attackers when using unsigned or self-signed Java code for exploitation. Now, if attackers choose to exploit Java vulnerabilities, even more social engineering will be required since users will need to not only open a malicious web page, but they will also need to click past the new security prompt prior to being exploited.
The code signing mechanism for Java code uses some of the principles as code signing used in app stores, such as the Windows 8 App Store or the Mac App Store. Code signing is a requirement in the app stores, while signing Java code merely prevents an alert shown to the user, but the choice to even show an alert is a step in the right direction for Java. To verify that a piece of software really was made by the author, a digital signature is applied to the software that is then run on the user’s system. With this security update from Oracle, attackers will need to either use a fraudulent certificate or acquire the ability to sign code on behalf of another entity, similar to what has been seen with certificate authorities like DigiNotar and Comodo being compromised for the same purpose. While a barrier is now posed to the attacker, users love clicking buttons, so it won’t stop determined users from being exploited. In any case, it will be easier to handle malware by simply revoking the fraudulent certificates, assuming Java properly leverages certificate revocations.
Needless to say, since these patches address vulnerabilities being exploited in the wild, it is critical that the patches are deployed as soon as possible.