Overlap dialling lets attacker shut down system
25 Oct 2016 at 22:30, Richard Chirgwin
In September, the popular open-source IP PBX project advised users to switch off its “overlap dialling” feature to dodge a possible denial-of-service (DoS) vulnerability.
Overlap dialling is designed to reduce call setup time, by letting the system start looking for destinations from an incomplete number.
The original bug report explained: “If this functionality is used with a device that has performed username/password authentication, RTP resources are leaked. This occurs because the code fails to release the old RTP resources before allocating new ones in this scenario. If all resources are used then RTP port exhaustion will occur and no RTP sessions are able to be set up.”
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