Erlang/OTP is a set of libraries for the Erlang programming language. In versions prior to OTP-27.3.4 (for OTP-27), OTP-26.2.5.12 (for OTP-26), and OTP-25.3.2.21 (for OTP-25), Erlang/OTP SSH fails to enforce strict KEX handshake hardening measures by allowing optional messages to be exchanged. This allows a Man-in-the-Middle attacker to inject these messages in a connection during the handshake. This issue has been patched in versions OTP-27.3.4 (for OTP-27), OTP-26.2.5.12 (for OTP-26), and OTP-25.3.2.21 (for OTP-25).
https://github.com/erlang/otp/security/advisories/GHSA-934x-xq38-hhqf
https://github.com/erlang/otp/releases/tag/OTP-27.3.4