A flaw was found in BusyBox's httpd web server. When configured with system password authentication, a user existence oracle may exist in certain build configurations. An attacker could distinguish existing from non-existing usernames by observing authentication failure behavior. Impact is limited to username enumeration and requires non-default compile options or uncommon password file states; default BusyBox builds with shadow password support are not affected.

A vulnerability was found in the BusyBox httpd Basic Authentication handler (networking/httpd.c) when configured to authenticate against system passwords. A missing else clause after a failed getspnamr() call creates an observable behavioral difference between authentication failures for existing and non-existing system users. Existing user with wrong password: connection reset. Non-existing user: clean HTTP 401.