Change effective on 07 November 2016
The Heroku Cedar-14 stack image has been updated with the most recent versions of installed packages. It addresses a range of cURL security vulnerabilities.
The new stack image will be rolled out automatically in the next 24 hours. You do not need to redeploy your app or restart your dynos.
See this Dev Center article for an overview of the libraries available on the Cedar-14 stack image.