Use common log message format and log level when user enters an invalid path. This unfortunately affects changes introduced in v2.11 to increase logging at default log level.
Security fixes:
- CVE-2020-14149: When entering an invalid directory with the FTP command CWD, a NULL ptr was deref. in a DBG() message even though the log level is set to a value lower than LOG_DEBUG. This caused uftpd to crash and cause denial of service. Depending on the init/inetd system used this could be permanent. (boo#1172959)