This has been fixed in 5.0.N with revision r114611. This fix needs to be merged to either 5.1 or 5.1.N
A bug has been found in Apache POI (all versions) that causes a data corruption if the input file hass less than 4 (OOXML 8) bytes.
This bug has been fixed by Alfresco and reported to Apache:
We maintain our own fork of the apache POI library that contains patches for bugs that did not yet made it into an official Apache POI release. The current version of this patch is: 3.10.1-20140922-alfresco-patched and can be found together with its sources in Nexus.
We need to create an updated version of this file and change the maven dependancies. The patch is attached to the Apache bug repoprt and this JIRA ticket.