The security alert accompanying the release says that another flaw (CVE-2013-0809) has also been patched, as both of these vulnerabilities may be remotely exploitable without authentication.
"Due to the severity of these vulnerabilities, and the reported exploitation of CVE-2013-1493 'in the wild,' Oracle strongly recommends that customers apply the updates provided by this Security Alert as soon as possible," the company advised.
Affected versions are Java JDK and JRE 7u15, 6u41, and 5.0u40 and all earlier versions of each.
Oracle software security assurance director Eric Maurice also added in a blog post that they intended to include a fix for CVE-2013-1493 in the April 16 Critical Patch Update for Java SE, but that they released the out-of-band patch because of the aforementioned reports of active exploitation.
In the meantime, Polish firm Security Explorations have unearthed half a dozen new zero-day Java flaws, most of them affecting Java SE 7. They have advised Oracle of their findings, and they are looking into it.
Oracle claims that one of the pointed out issues cannot be considered a security flaw as it demonstrates "allowed behavior."
Security Explorations disagrees. "There is a mirror case corresponding to Issue 54 that leads to access denied condition and a security exception. That alone seems to be enough to contradict the 'allowed behavior' claim by the company," wrote CEO Adam Gowdiak on the Full Disclosure mailing list. "If Oracle sticks to their assessment we'll have no choice than to publish details of Issue 54."