Vulnerability details

Key Exchange without Entity Authentication vulnerability in Erlang/OTP ssl allows a peer that answers a TLS 1.3 client connection to impersonate the intended server. A pre_shared_key extension in the ServerHello that the client never offered causes the client to complete the handshake without validating the server's certificate, so ssl:connect returns {ok, Socket} against a peer holding no certificate, no private key and no prior session. tls_client_connection_1_3:handle_server_hello/2 passes the received extension to tls_gen_connection_1_3:handle_resumption/2, which sets resumption = true on its mere presence without checking that the client offered a PSK. tls_handshake_1_3:get_pre_shared_key/4 meanwhile falls back to the all-zero "no PSK" value and keys the handshake with the ordinary non-PSK schedule, so the attacker's own ephemeral key suffices. The resumption flag then routes maybe_resumption/1 straight to wait_finished, skipping the certificate-handling states, so certificate path validation, verify_fun, hostname verification, partial_chain, CRL checking and OCSP stapling are all bypassed. The default client configuration is affected; clients restricted to TLS 1.2 are not. This issue affects OTP from OTP 22.2 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1, corresponding to ssl from 9.5 before 11.2.12.13, 11.6.0.6, and 11.7.7.

• https://github.com/erlang/otp/security/advisories/GHSA-rgxr-4g4w-j875 relatedvendor-advisory
• https://cna.erlef.org/cves/CVE-2026-89422.html related
• https://osv.dev/vulnerability/EEF-CVE-2026-89422 related
• https://www.erlang.org/doc/system/versions.html#order-of-versions x_version-scheme
• https://github.com/erlang/otp/commit/21b8a1b0ad0adf200682b3854bc50114ab2b8c62 related
• https://github.com/erlang/otp/commit/afec5156361bb50d3607c7c1a453c19b9149b324 patch
• https://github.com/erlang/otp/commit/98c66c858113949c4262d26cd7d426c4b09d2b35 patch
• https://github.com/erlang/otp/commit/fd1d9d07fc92ec0d59f96dfb66182195882bb7dd patch