h2o -- directory traversal vulnerability

Yakuzo reports:

H2O (up to version 1.4.4 / 1.5.0-beta1) contains a flaw in its URL
normalization logic.
When file.dir directive is used, this flaw
allows a remote attacker to retrieve arbitrary files that exist
outside the directory specified by the directive.
H2O version 1.4.5 and version 1.5.0-beta2 have been released
to address this vulnerability.
Users are advised to upgrade their servers immediately.
The vulnerability was reported by: Yusuke OSUMI.