CVE-2026-55950— DTLS listener crash via race condition in dtls_packet_demux causes denial of service for all sessions

DTLS listener crash via race condition in dtls_packet_demux causes denial of service for all sessions

Time-of-check Time-of-use (TOCTOU) race condition vulnerability in Erlang/OTP ssl (dtls_packet_demux module) allows an unauthenticated remote attacker to crash all active DTLS sessions on a listener. A DTLS server listener uses a single shared dtls_packet_demux gen_server process to route incoming UDP datagrams to the correct connection handler. When a DTLS client reconnects rapidly from the same source address and port (sending multiple ClientHello messages in quick succession), a race condition in the demux's internal gb_trees key-value store causes a {key_exists, {old, Client}} crash, terminating the demux process. Because the demux is shared across all DTLS associations on that listener, its crash immediately kills every active DTLS session, not just the attacker's. The attack is pre-authentication: the attacker only needs to send UDP datagrams containing valid ClientHello messages from the same source IP and port before the intermediate DOWN monitor message is processed by the gen_server. No credentials, no completed handshake, and no special configuration are required, and the crash can be repeated indefinitely to create a persistent denial of service for all clients of that listener. This vulnerability is associated with program file lib/ssl/src/dtls_packet_demux.erl. This issue affects OTP from OTP 25.3 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 10.9 before 11.7.3, 11.6.0.3 and 11.2.12.10.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

检查时间与使用时间(TOCTOU)的竞争条件

Erlang/OTP 竞争条件问题漏洞

erlang erlang/otp是erlang社区开源的一套并发编程语言及运行时系统。 Erlang/OTP存在竞争条件问题漏洞，该漏洞源于ssl的dtls_packet_demux模块存在Time-of-check Time-of-use (TOCTOU)竞争条件问题，可能导致未经身份验证的远程攻击者崩溃监听器上所有活动的DTLS会话。

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