RFC 10015 makes finite-field Diffie-Hellman and RSA key exchange MUST NOT in TLS 1.2 and DTLS 1.2

Sources: RFC 10015, HN discussion
Summary: RFC 10015, published in July 2026, sets finite-field Diffie-Hellman and RSA key exchange to MUST NOT in TLS 1.2 and DTLS 1.2. The document updates seventeen RFCs: 4162, 4279, 4346, 4785, 5246, 5288, 5289, 5469, 5487, 5932, 6209, 6347, 6367, 6655, 7905, 8422 and 9325. One of those, RFC 9325, is part of BCP 195 alongside RFC 8996, so the change reaches BCP 195 through that document rather than updating BCP 195 directly.
Why it matters: TLS 1.2 cipher-suite allowlists that still carry DHE or RSA key exchange are now non-conformant and need review.