This is very unlikely. Any ISP with some experience will make sure customers are not able to interact any more than they could from outside the network. That's network 101.
Having worked for large ISP's for around a decade, cheap comes first, customer safety comes last.
Also, QUIT BREAKING THE INTERNET. CGNAT is complete crap that breaks the internet peer model. Even ISPs not using CGNAT are pushing complete crap on users. For example last week I had a user that VOIP stopped working. They received a new integrated cable modem router from their ISP. If you rebooted the unit VOIP worked about an hour, after that it would stop passing VOIP packets (ran tcpdump on the server and watched them stop). If we ran VOIP over another port it would work (but had different issues related to changing around 50 phones so we only used it for testing). There were no options to disable SIP_NAT, nor any other settings that would fix the problem. Since this ISP also provided their own phone service I found the whole debacle rather anti-competitive. They simply have no interest in contacting the modem vendor and having them fix the problem.
We ended up supplying our own modem and router in this case and the problem was resolved.
Also, QUIT BREAKING THE INTERNET. CGNAT is complete crap that breaks the internet peer model. Even ISPs not using CGNAT are pushing complete crap on users. For example last week I had a user that VOIP stopped working. They received a new integrated cable modem router from their ISP. If you rebooted the unit VOIP worked about an hour, after that it would stop passing VOIP packets (ran tcpdump on the server and watched them stop). If we ran VOIP over another port it would work (but had different issues related to changing around 50 phones so we only used it for testing). There were no options to disable SIP_NAT, nor any other settings that would fix the problem. Since this ISP also provided their own phone service I found the whole debacle rather anti-competitive. They simply have no interest in contacting the modem vendor and having them fix the problem.
We ended up supplying our own modem and router in this case and the problem was resolved.