Why is this C code vulnerable?

Question

I’ve been doing some code analysis exercises and came across an interesting case. The exercise presents a C code with a function and asks what type of attack this code is vulnerable to. I couldn’t identify anything beyond the gets function (which can be exploited for buffer overflow attacks). Is there any other piece of code that contains some vulnerability?

int crack_code()
{ 
    char code[10];
    int val=999, i;
    
    printf("Enter code: "); 
    gets(code);
    
    for (i=0; i<10; i+=2)
    {
        val = (val & code[i]) | code[i+1];
        val &= val >> code[i];
    } 
    
    if (val == 101)
    {
        return 0;
    } else
    {
        return 1;
    }
} 

void main()
{
    if (crack_code())
    {
        printf("Crack the secret code!\n");
    }
    else {
        printf("Now you know the secret!\n");
    }
}

Thank you so much for anyone who can contribute!