Selfhosted

Does creating a VPN into my home network using my router increase my attack surface?

Yes, but it also provides the ability to access any resource in your network in a secure way.

It is typically less safe to expose 3 or 4 different services you want remote access than a single VPN daemon that is actually designed for that specific scenario and has mitigations for common attacks built in.

To make your setup secure you can consider a few steps:

• Use Wireguard: don't be afraid to expose the Wireguard port because if someone tries to connect and they don’t authenticate with the right key the server will silently drop the packets. An attacker won't even know there's something listening on that port / it will be invisible to typical IP scans / / will ignore any piece of traffic that isn’t properly encrypted with your keys;
• Use a 5-digit port for your VPN - something like 23901 (up to 65535) will be way harder to find than typical ports like the default 51820 or 443;
• Go full paranoid and use a firewall to restrict what countries or even days, hours access your server is allowed. Eg. only allow incoming connection from your country (https://wiki.nftables.org/wiki-nftables/index.php/GeoIP_matching). Be aware of what happens when you're abroad;
• Don't port forward IPv6 if you don't need it. Might be easier than dealing with a dual stack firewall and/or other complexities.

In a side note: a VPN doesn't mean full access to your network either. You can setup a VPN endpoint that only allows access to a few specified services running on specific machines instead of the entire network. This will give you extra security if you're into that.

• https://www.digitalocean.com/community/tutorials/how-to-set-up-wireguard-on-debian-11 (skip IPv6)
• https://github.com/ngoduykhanh/wireguard-ui - good UI to manage wg
• https://wiki.nftables.org/wiki-nftables/index.php/Quick_reference-nftables_in_10_minutes
• https://tadeubento.com/2024/nftables-country-geo-blocking/

Opening any service / port has a impact to security in your network. Vpns are meant to be exposed and are generally secure. As long as your router updates and fixes security issues there shouldn't be an issue with the router providing the VPN.

If you're worried about that, I can recommend a service like Tailscale which does not require permanently open ports to the outside world, offering quite a bit more security than an exposed traditional VPN server.

Does it increase your attack surface? Yes. With proper precautions is this level of risk negligible? Also yes.

You will be opening a port to the outside world. Anyone can try to use it. But if you are using key authentication it will be fine.

Increase the attack surface compared to what? If you don't allow/enable any access to services inside your network from outside, then by definition you have fewer attack surfaces than if you add a VPN to that empty list.

So trivially the answer is "yes, it adds an attack surface".

But what are the alternatives? If you directly expose each individual service on a dedicated port, for example, then you'd add many more (and usually less well hardened) attack surfaces instead.

So if the comparison is "expose 5 web-based services directly" vs. "expose one VPN like wireguard", then the second option is almost always the clear winner when it comes to security (and frequently also when it comes to ease of setup as well as comfort).