CVE-2026-63569 — MTI/A0 DHAgreement does not validate the peer's ephemeral value

Improper input validation in DHAgreement.CalculateAgreement in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 can allow an on-path attacker to make the local party compute an agreed value already known to the attacker, defeating the key authentication intended by MTI/A0. Only applications that call DHAgreement directly are affected.