FWIW with this in /etc/cyrus.conf
https cmd="httpd -s -U 30" listen="mail.xxxxxx.com:8443" prefork=0 maxchild=100
and using a browser to surf to https://mail.xxxxxx.com:8443/rss/ I get the below in the logs...
Mar 07 16:01:48 mail cyrus/https[8254]: mail.xxxxxx.org [120.88.xxx.xxx] as "admin@xxxxxxxxxx" with "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/
537.36 (KHTML, like Gecko) Chrome/88.0.4324.152 Safari/537.36" via SESSIONID=<cyrus-1615096908-8254-1-4224126592648939708>; "GET /rss/ HTTP/2" (auth=B
asic) => "HTTP/2 200 OK" (stream-id=1; tx-encoding=chunked; cnt-encoding=br) [timing: cmd=0.007623 net=0.000023 total=0.007646]
Mar 07 16:01:48 mail cyrus/master[8166]: process type:SERVICE name:https path:/usr/lib/cyrus/bin/httpd age:0.104s pid:8254 signaled to death by signal
11 (Segmentation fault)
Mar 07 16:01:48 mail kernel: httpd[8254]: segfault at 7ffdaf0764c8 ip 000055c5eac42e91 sp 00007ffdaf0764c8 error 6 in httpd[55c5eabf8000+dc000]
Mar 07 16:01:48 mail kernel: Code: f0 fb ff 31 f6 48 89 c7 e8 9c c9 fb ff 48 89 05 6d fc 0c 00 48 89 c3 eb b1 41 57 41 56 41 55 41 54 55 53 48 81 ec 0
0 10 00 00 <48> 83 0c 24 00 48 81 ec 28 02 00 00 48 8b 5e 08 64 48 8b 04 25 28
537.36 (KHTML, like Gecko) Chrome/88.0.4324.152 Safari/537.36" via SESSIONID=<cyrus-1615096908-8254-1-4224126592648939708>; "GET /rss/ HTTP/2" (auth=B
asic) => "HTTP/2 200 OK" (stream-id=1; tx-encoding=chunked; cnt-encoding=br) [timing: cmd=0.007623 net=0.000023 total=0.007646]
Mar 07 16:01:48 mail cyrus/master[8166]: process type:SERVICE name:https path:/usr/lib/cyrus/bin/httpd age:0.104s pid:8254 signaled to death by signal
11 (Segmentation fault)
Mar 07 16:01:48 mail kernel: httpd[8254]: segfault at 7ffdaf0764c8 ip 000055c5eac42e91 sp 00007ffdaf0764c8 error 6 in httpd[55c5eabf8000+dc000]
Mar 07 16:01:48 mail kernel: Code: f0 fb ff 31 f6 48 89 c7 e8 9c c9 fb ff 48 89 05 6d fc 0c 00 48 89 c3 eb b1 41 57 41 56 41 55 41 54 55 53 48 81 ec 0
0 10 00 00 <48> 83 0c 24 00 48 81 ec 28 02 00 00 48 8b 5e 08 64 48 8b 04 25 28
