I put vulnerability in quotes because it’s looking less like a problem. (Correct me if I’m wrong.) Here’s the situation. Both Sans and Mozilla have failed to duplicate the crash although have duplicated extremely slow browser performance. Here’s the official response from mozilla.org…
We have investigated this issue and can find no basis for claims that variants of this denial-of-service attack can cause an exploitable crash, and no evidence for this claim has been offered. There does not appear to be any risk to users or their computers beyond the temporary unresponsiveness at startup.