You are probably already aware of this announcement, but I thought it prudent to post anyway. Apparently, Juniper somehow released a vulnerable ScreenOS, versions 6.2.0r15 through 6.2.0r18 and 6.3.0r12 through 6.3.0r20. And, had now released a patch. Juniper claims the exploit has not been reported as exploited by customers. But, it’s unclear how customer would know they would have been exploited..
In any case, customers should be upgrading to ScreenOS 6.2.0r19 or 6.3.0r21; both of which have received the fix. See this bulletin for further information regarding which devices are affected and how to upgrade them:
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10713&cat=SIRT_1&actp=LIST
For further information, see this announcement from Juniper:
http://forums.juniper.net/t5/Security-Incident-Response/Important-Announcement-about-ScreenOS/ba-p/285554