Correction to original report - it doesn't hang indefinitely, it just takes a really long time. Specifically, looks like it's quadratic in the length of the input string. Increase the size of the input string to 1000*1000 and it's really really slow. 

I don't know for sure if it's possible to implement regexes in a way that avoids this pathological behaviour, but it's certainly quite risky that an otherwise working bit of code using a pattern containing .* can hang/livelock an application for an arbitrary  amount of time if passed a larger-than-expected (but actually not that big) input string.