Users that have a route that contains the string ":controller" are susceptible to objects being leaked globally which can lead to unbounded memory growth. To identify if your application is vulnerable, look for routes that contain ":controller".
Internally, Action Pack keeps a map of "url controller name" to "controller class name". This map is cached globally, and is populated even if the controller class doesn't actually exist.
All users running an affected release should either upgrade or use one of the workarounds immediately.
The FIXED releases are available at the normal locations.
There are no feasible workarounds for this issue.
To aid users who aren't able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.
Please note that only the 4.1.x and 4.2.x series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases.