How to propagate critical fixs from master to develope branch.

[Mgr Georg Black]

Hello everyone.I red git manual but I can't figure out how to propagate 
critical change from master branch to long live develop branch. I red chapter 
about rebasing that I think could solve it but at the end of this chapter is 
written that it's not recommended for pubic repositories. I don't know how to 
do it without merging develop branch to master.
I'll appreciate list of orders very much. :-)
Thanks for any info or link.
GB