Hello,
today after updating my system, dnf started segfaulting. I debugged it
a bit and found out that it is not dnf/libdnf's fault, but glibc's[0].
If dnf started crashing for you, just use --refresh in command-line or
downgrade glibc from -29 to -28.
[0]
https://bugzilla.redhat.com/show_bug.cgi?id=1417870
--
-Igor Gnatenko