There is a new pull request by ericonr against master on the void-packages repository

https://github.com/ericonr/void-packages mdbook
https://github.com/void-linux/void-packages/pull/24309

mdBook: update to 0.4.2.
Tested on x86_64 with void-docs.

A patch file from https://github.com/void-linux/void-packages/pull/24309.patch is attached