VTech Storio Max before 56.D3JM6 allows remote command execution via shell metacharacters…

Summary

VTech Storio Max before 56.D3JM6 allows remote command execution via shell metacharacters in an Android activity name. It exposes the storeintenttranslate.x service on port 1668 listening for requests on localhost. Requests submitted to this service are checked for a string of random characters followed by the name of an Android activity to start. Activities are started by inserting their name into a string that is executed in a shell command. By inserting metacharacters this can be exploited to run arbitrary commands as root. The requests also match those of the HTTP protocol and can be triggered on any web page rendered on the device by requesting resources stored at an http://127.0.0.1:1668/ URI, as demonstrated by the http://127.0.0.1:1668/dacdb70556479813fab2d92896596eef?';{ping,example.org}' URL.