wu-ftpd contains a flaw that may allow a malicious user to overwrite arbitrary files. The issue is triggered when an attacker sends a specially formed rnfr command. It is possible that the flaw may allow the attacker to overwrite any file on the system as root resulting in a loss of integrity.
Upgrade to version 2.4.2 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.