The ADDW macro in stdio-common/vfscanf.c in the GNU C Library (aka glibc or libc6) before 2.21 does not properly consider data-type size during memory allocation, which allows context-dependent attackers to cause a denial of service (buffer overflow) or possibly have unspecified other impact via a long line containing wide characters that are improperly handled in a wscanf call.
http://openwall.com/lists/oss-security/2015/02/04/1
http://seclists.org/fulldisclosure/2019/Jun/18
http://seclists.org/fulldisclosure/2019/Sep/7
http://www.oracle.com/technetwork/security-advisory/cpujan2018-3236628.html
http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
http://www.securityfocus.com/bid/72428
http://www.ubuntu.com/usn/USN-2519-1
https://seclists.org/bugtraq/2019/Jun/14
https://seclists.org/bugtraq/2019/Sep/7