[Newbie alert] curl not working, need ca-bundle?

[cescoc]

Hi everybody!
Sorry in advance if my question (as well as my english) sounds annoying or if it has been answered before, but I'm a newbie and after several nights spent googling for it I'm a little frustrated not being able to solve the problem by myself.

How does curl command is supposed to work on merlin build? I've installed curl via entware but everytime I try to use it I get the following message:

curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: http://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
 the bundle, the certificate verification probably failed due to a
 problem with the certificate (it might be expired, or the name might
 not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
 the -k (or --insecure) option.

I've had my RT-N66U running THIS for a long time, but since Dropbox has recently made slight changes to its API I had to update dropbox-uploader to the last commit on GitHub and it's not working anymore.

I'm pretty sure the problem is caused by the missing certificates for curl because everything run smooth with the -k parameter.

I'm not an expert and I'm not sure on the best practices in terms of security, but how I'm supposed to add CA bundle certificates in order to make curl work?

I've looked for ca-certificates package as mentioned HERE but the package doesn't seem to be available anymore and I have no idea on how to manually add certificates in asuswrt.

Thank you, your help is much appreciated!

Cesare