Integer overflow in the valid_user_field function in journal/journald-native.c in systemd allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a large journal data field, which triggers a heap-based buffer overflow.
https://security.gentoo.org/glsa/201612-34
https://bugzilla.redhat.com/show_bug.cgi?id=859051
http://www.openwall.com/lists/oss-security/2013/10/01/9