This is precisely why we rebase and squash. We maintain about 4 release branches at any given point and having everything squashed into one or two commits makes a bug fix on master simple and straightforward to downstream.

Although more frequently what we will do is do the bug fix on the furthest downstream branch and because we tag our branches with semver scheme we jus have our prep-for-deploy build automatically walk back up the branches back to master and attempt to merge the feature in along the way.