As reported by WinRumors, Microsoft's range of Windows Phones suffer from a denial-of-service attack bug that allows attackers to reboot the device and disable the messaging functionality on a device. According to the article, it's enough to send a simple and prepared SMS text message which forces Windows Phone 7.5 smartphones to reboot and kills the Messaging Hub functionality after which means it will not open despite repeat attempts. WinRumors has tested the attack on a range of Windows Phone devices, including HTC's Titan and Samsung's Focus Flash. Some devices were running the the latest 7740 version of Windows Phone 7.5, others were on Mango RTM 7720 builds.
According to their findings, this vulnerability is not device specific but it seems it's related to the Windows Phone Messaging Hub in general and the way it handles messages because the same behavior can also be triggered if a user sends a Facebook chat message or Windows Live Messenger message to a Windows Phone.
WinRumors hasn't published the SMS code in question but said they are in contact with Microsoft but mentions that there seems to be no workaround-fix at the moment. This means, users have to hardreset their device to get it back to work. Not yet confirmed is if this bug is related to Windows Phone 7.5/Mango devices only or related to Windows Phone in general.
Cheers ~ Arne