[FREEBSD:06ED6A49-BAD4-11EC-9CFE-0800270512F4] Ruby -- Buffer overrun in String-to-Float conversion

piao reports:

    Due to a bug in an internal function that converts a String
    to a Float, some convertion methods like Kernel#Float
    and String#to_f could cause buffer over-read.
    A typical consequence is a process termination due to
    segmentation fault, but in a limited circumstances, it may
    be exploitable for illegal memory read.