pq-split-dropped
The server is post-quantum, but a PQ ClientHello split across two TCP segments gets no answer. Real clients’ PQ hellos are often split, so something in the path, usually a load balancer or firewall, will fail some of them.
The verdict is pqWithWarning: post-quantum, with this warning in the report.
How pqdoctor sees it
Section titled “How pqdoctor sees it”- The PQ hello in one piece (probe 2) negotiates
X25519MLKEM768. - The same hello split across two segments (probe 5) gets no reply.
The fix
Section titled “The fix”Find the device in front of the server that can’t reassemble a split ClientHello, and update it or turn off its TLS inspection for this traffic.
Shown in the fix lab
Section titled “Shown in the fix lab”A post-quantum OpenSSL 3.5 server behind a box that drops ClientHellos split across TCP segments was reported “PQ + warning”. With the box removed, it was post-quantum with no warning.
From Workers
Section titled “From Workers”The Workers version writes the two halves 40 ms apart, but whether they leave Cloudflare’s network as separate TCP segments can’t be observed locally. So this warning may not reproduce from Workers.
In the study
Section titled “In the study”No origin in the study got this cause.