int ssl_security_cert_chain(SSL *s, STACK_OF(X509) *sk, X509 *x, int vfy)
{
    int rv, start_idx, i;
    if (x == NULL) {
        x = sk_X509_value(sk, 0);
        start_idx = 1;
    } else
        start_idx = 0;

    rv = ssl_security_cert(s, NULL, x, vfy, 1);
    if (rv != 1)
        return rv;

    for (i = start_idx; i < sk_X509_num(sk); i++) {
        x = sk_X509_value(sk, i);
        rv = ssl_security_cert(s, NULL, x, vfy, 0);
        if (rv != 1)
            return rv;
    }
    return 1;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.