Language: C
Label: safe
CWE: CWE-78 \u2014 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

Code:
valid_hostname(const char *s)
{
	size_t i;

	if (*s == '-')
		return 0;
	for (i = 0; s[i] != 0; i++) {
		if (strchr("'`\"$\\;&<>|(){}", s[i]) != NULL ||
		    isspace((u_char)s[i]) || iscntrl((u_char)s[i]))
			return 0;
	}
	return 1;
}