TL;DR
- Port 853 (DoT and DoQ) now offers hybrid post-quantum key exchange, X25519MLKEM768, like DoH and DoH3 on port 443. Clients that do not offer it still get X25519.
- Since 22 October 2026 at 17:33 (UTC+3). dnsdist now runs a build with OpenSSL 4.0.3 for DoT and quiche on BoringSSL for DoQ. Nothing changes for clients: same address, same ports, no reconfiguring.
- Checked from a second server on 24 October, reading each ServerHello in a packet capture: 8 of 8 DoT and 8 of 8 DoQ connections that offered the hybrid group got it, and 8 of 8 of each that offered only X25519 got X25519.
- This closes a gap we corrected in public. From 27 September, when dnsdist took over port 853, until 22 October, DoT and DoQ offered only X25519. We found it on 19 October and corrected the pages that said otherwise.
The gap came with the move to dnsdist. Its DoT was linked against a TLS library with no ML-KEM, and the TLS defaults of its DoQ library did not include the hybrid group, so port 853 used classical key exchange while port 443 kept the hybrid. The new build links DoT against OpenSSL 4.0.3 and builds DoQ on quiche with BoringSSL, both offering X25519MLKEM768 by default. The recipe, with pinned versions and a check that the right libraries are actually loaded, is public in dnsdoh-edge.
No common DNS client lets you pin the key exchange group for DoT or DoQ, so the check is to read the server’s choice off the wire: in TLS 1.3 the ServerHello names it in the clear, as group 4588 for the hybrid and 29 for X25519. For DoQ, tell tshark that port 853 is QUIC with -d udp.port==853,quic. The commands, and the 19 October correction with this update under it, are in the post-quantum key exchange guide. The per-transport summary is on the protocols page.