The vulnerability is a time-of-check to time-of-use (TOCTOU) race condition in the dtls_packet_demux gen_server process used by Erlang/OTP's DTLS server listener. When a client rapidly reconnects from the same source address and port, sending multiple ClientHello messages in quick succession, a race condition in the internal gb_trees key-value store causes a {key_exists, {old, Client}} crash. This crash terminates the shared demux process, which routes incoming UDP datagrams to connection handlers, thereby killing all active DTLS sessions on that listener. The attack requires no credentials or completed handshake and can be repeated indefinitely to maintain denial of service. The issue affects OTP versions from 25.3 before 29.0.3, 28.5.0.3, and 27.3.4.14, corresponding to ssl versions 10.9 before 11.7.3, 11.6.0.3, and 11.2.12.10.

An unauthenticated remote attacker can cause a denial of service by crashing the shared dtls_packet_demux process, which immediately terminates all active DTLS sessions on the affected listener. This disrupts all clients connected to that listener, not just the attacker, potentially causing widespread service interruption.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the current data. Until a patch is available, consider mitigating by limiting rapid reconnections from the same source IP and port if possible, though no specific vendor guidance is given.