atftp is vulnerable to denial of service (DoS). The vulnerability exists as it does not lock the thread_list_mutex
mutex before assigning the current thread data structure. As a result, the daemon is vulnerable to a denial of service attack due to a NULL pointer dereference. If thread_data is NULL when assigned to current, and modified by another thread before a certain tftpd_list.c check, there is a crash when dereferencing current->next.
lists.debian.org/debian-lts-announce/2019/05/msg00012.html
pulsesecurity.co.nz/advisories/atftpd-multiple-vulnerabilities
seclists.org/bugtraq/2019/May/16
security.gentoo.org/glsa/202003-14
sourceforge.net/p/atftp/code/ci/382f76a90b44f81fec00e2f609a94def4a5d3580/
usn.ubuntu.com/4540-1/
www.debian.org/security/2019/dsa-4438