mysqld_safe is vulnerable to privilege escalation attacks. The flaw was found in the way the mysqld_safe script handled creation of error log file. A local authenticated user could use this flaw to escalate their privileges to root.
legalhackers.com/advisories/MySQL-Maria-Percona-RootPrivEsc-CVE-2016-6664-5617-Exploit.html
packetstormsecurity.com/files/139491/MySQL-MariaDB-PerconaDB-Root-Privilege-Escalation.html
rhn.redhat.com/errata/RHSA-2016-2130.html
rhn.redhat.com/errata/RHSA-2016-2749.html
seclists.org/fulldisclosure/2016/Nov/4
www.debian.org/security/2017/dsa-3770
www.oracle.com/technetwork/security-advisory/cpuoct2016-2881722.html
www.oracle.com/technetwork/security-advisory/cpuoct2016-2881722.html#AppendixMSQL
www.securityfocus.com/archive/1/539695/100/0/threaded
www.securityfocus.com/bid/93612
access.redhat.com/errata/RHSA-2017:2192
access.redhat.com/errata/RHSA-2018:0279
access.redhat.com/errata/RHSA-2018:0574
access.redhat.com/security/cve/CVE-2016-6663
access.redhat.com/security/cve/CVE-2016-6664
access.redhat.com/security/updates/classification/#important
bugzilla.redhat.com/show_bug.cgi?id=1386562
dev.mysql.com/doc/relnotes/mysql/5.5/en/news-5-5-51.html
dev.mysql.com/doc/relnotes/mysql/5.5/en/news-5-5-52.html
rhn.redhat.com/errata/RHSA-2016-2130.html
security.gentoo.org/glsa/201702-18
www.exploit-db.com/exploits/40679/
www.percona.com/blog/2016/11/02/percona-responds-to-cve-2016-6663-and-cve-2016-6664/