In imap_scan_tree_recursive in Claws Mail through 3.17.6, a malicious IMAP server can trigger stack consumption because of unlimited recursion into subdirectories during a rebuild of the folder tree.
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3CRKHUOVTJBHT53J4CYU53PXYYQKSGEA/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JUBLHUG2UCXVABAGN5FVTD3AB3YKE5NN/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YNJIXYDMSXYDII4ERMQ4EEKZX64U3QR4/
www.thewildbeast.co.uk/claws-mail/bugzilla/show_bug.cgi?id=4313