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 a risk-management decision for use of the alloca function, which might allow context-dependent attackers to cause a denial of service (segmentation violation) or overwrite memory locations beyond the stack boundary via a long line containing wide characters that are improperly handled in a wscanf call.
Exploitability
AV:NAC:LAu:NImpact
C:NI:PA:P6.4/AV:N/AC:L/Au:N/C:N/I:P/A:P