Although pretty late, but CyanogenMod has now included a patch for Stagefright vulnerability in the latest nightly builds for CM12.1 and CM10.1. The new builds are already available for download, you can grab these builds from your device’ section over at get.cm.
For the unknown, Stagefright vulnerability is a serious security bug on Android that let’s an attacker gain access to files on your device, as well as its camera and microphone, all through a MMS message that you may not even notice.
This is a serious security bug and we strongly recommend you to update your devices to the latest CM 12.1/10.1 nightly build for your device.
As for the stable releases, well CyanogenMod has stated that stable releases will be coming with Stagefright patch for version 11.0, 12.0 (and of course 12.1) by the end of August 2015.