Time-of-check Time-of-use (TOCTOU) Race Condition in otp - CVE-2026-55950

Vulnerability identifier: #VU136824

CSH Severity: Medium

CVSS v4: 8.7 [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]

CVE-ID: CVE-2026-55950

CWE-ID: CWE-367

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to a time-of-check time-of-use race condition in the dtls_packet_demux gen_server process when handling rapid DTLS client reconnects from the same source address and port. A remote attacker can send multiple valid ClientHello datagrams in quick succession to cause a denial of service.

The crash of the shared demultiplexing process terminates all active DTLS sessions on the affected listener, and no completed handshake or credentials are required.

otp
openEuler
erlang-syntax_tools
erlang-edoc
erlang-diameter
erlang-dialyzer
erlang-debugsource
erlang-debuginfo
erlang-debugger
erlang-crypto
erlang-compiler
erlang-common_test
erlang-asn1
erlang
erlang-xmerl
erlang-wx
erlang-tools
erlang-tftp
erlang-eldap
erlang-stdlib
erlang-ssl
erlang-ssh
erlang-src
erlang-snmp
erlang-sasl
erlang-runtime_tools
erlang-reltool
erlang-public_key
erlang-parsetools
erlang-os_mon
erlang-odbc
erlang-observer
erlang-mnesia
erlang-megaco
erlang-kernel
erlang-jinterface
erlang-inets
erlang-ftp
erlang-examples
erlang-eunit
erlang-et
erlang-erts
erlang-erl_interface
erlang-erl_docgen

Install security update from vendor's website.

otp - addressed in versions 27.3.4.14, 28.5.0.3, 29.0.3
erlang-syntax_tools - update to 25.3.2.6-18
erlang-edoc - update to 25.3.2.6-18
erlang-diameter - update to 25.3.2.6-18
erlang-dialyzer - update to 25.3.2.6-18
erlang-debugsource - update to 25.3.2.6-18
erlang-debuginfo - update to 25.3.2.6-18
erlang-debugger - update to 25.3.2.6-18
erlang-crypto - update to 25.3.2.6-18
erlang-compiler - update to 25.3.2.6-18
erlang-common_test - update to 25.3.2.6-18
erlang-asn1 - update to 25.3.2.6-18
erlang - update to 25.3.2.6-18
erlang-xmerl - update to 25.3.2.6-18
erlang-wx - update to 25.3.2.6-18
erlang-tools - update to 25.3.2.6-18
erlang-tftp - update to 25.3.2.6-18
erlang-eldap - update to 25.3.2.6-18
erlang-stdlib - update to 25.3.2.6-18
erlang-ssl - update to 25.3.2.6-18
erlang-ssh - update to 25.3.2.6-18
erlang-src - update to 25.3.2.6-18
erlang-snmp - update to 25.3.2.6-18
erlang-sasl - update to 25.3.2.6-18
erlang-runtime_tools - update to 25.3.2.6-18
erlang-reltool - update to 25.3.2.6-18
erlang-public_key - update to 25.3.2.6-18
erlang-parsetools - update to 25.3.2.6-18
erlang-os_mon - update to 25.3.2.6-18
erlang-odbc - update to 25.3.2.6-18
erlang-observer - update to 25.3.2.6-18
erlang-mnesia - update to 25.3.2.6-18
erlang-megaco - update to 25.3.2.6-18
erlang-kernel - update to 25.3.2.6-18
erlang-jinterface - update to 25.3.2.6-18
erlang-inets - update to 25.3.2.6-18
erlang-ftp - update to 25.3.2.6-18
erlang-examples - update to 25.3.2.6-18
erlang-eunit - update to 25.3.2.6-18
erlang-et - update to 25.3.2.6-18
erlang-erts - update to 25.3.2.6-18
erlang-erl_interface - update to 25.3.2.6-18
erlang-erl_docgen - update to 25.3.2.6-18

• https://github.com/erlang/otp/security/advisories/GHSA-hwfc-5hf4-gvr3

• Multiple vulnerabilities in otp
• openEuler 24.03 LTS SP1 update for erlang
• openEuler 24.03 LTS SP4 update for erlang
• openEuler 24.03 LTS SP3 update for erlang