The bug is does not seem to affect all versions of iOS and there is a fairly simple work around if you do get the nasty message sent to you. The most simple is to just have someone send you another text which seems to cancel out the bad one. Apple is apparently aware of the issue, but has not released a fix for it just yet.
The bug has been making the rounds on Twitter with people posting about how easy it is to run. As of this writing the only semi-confirmed exclusions are iOS 8.4 and some jailbroken phones. Why a jailbroken iPhone would not be affected is a mystery, but there are several people claiming immunity to the bug on a jailbroken version of iOS8.x.
The actual vulnerability has to do with the way the OS tries to display the Unicode text in the banner notification area. It seems that the OS gives up after attempting to display is over and over. This is what causes the initial reboot.