This issue also affects users of CyanogenMod 11 which is currently based on Android 4.4.4 (https://jira.cyanogenmod.org/browse/CYAN-5728). The same thing happened to the HTC One M7, but HTC fixed it quickly with an OTA update (http://venomroms.com/venomhub-fix-no-sound-calls-htc-one-m7). All in all it looks like the malfunction is caused by an automatic update of the Google Play Services framework. Not reacting at all so far is definitively not a good move of Google.