Weird behaviour in wildcard CNAME - is this feature or bug? Can it be changed?

[Petr Bena]

Hello,

I observed very weird behaviour that I can reproduce on both these BIND9 
versions:

BIND 9.11.4-P2-RedHat-9.11.4-9.P2.el7 (Extended Support Version) 
<id:7107deb> (slave)

BIND 9.8.2rc1-RedHat-9.8.2-0.68.rc1.el6_10.1 (master)

Someone has created a wildcard CNAME:

*.prod.app.pcp.cn.prod.     300     IN     CNAME 
gs-vip.prod-wq-01.k8s.pcp.cn.prod.

Which was working just fine, everything behind this wildcard was working 
as a CNAME:

# dig test.prod.app.pcp.cn.prod +short
gs-vip.prod-wq-01.k8s.pcp.cn.prod.

But moment when someone has created another record (CNAME as well) behind it

funding-gw.payis.prod.app.pcp.cn.prod.     30     IN     CNAME 
gs-vip.prod-wq-01.k8s.pcp.cn.prod.

Records that are anywhere in the path of this new record stopped 
working, for example

payis.prod.app.pcp.cn.prod        would NOT work

test.payis.prod.app.pcp.cn.prod would NOT work

test.prod.app.pcp.cn.prod          would work


Why is this? Is that normal or a bug?