A heap-based buffer overflow exists in GNU Bash before 4.3 when wide characters not supported by the current locale set in the LC_CTYPE environment variable are printed through the echo built-in function. A local attacker who can provide data to print through the \echo -e\ built-in function may use this flaw to crash a script or execute code with the privileges of the bash process. This occurs because ansicstr() in lib/sh/strtrans.c mishandles u32cconv().