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/27660

mdBook: update to 0.4.5.
Fixes CVE-2020-26297

A patch file from https://github.com/void-linux/void-packages/pull/27660.patch is attached