npm access token alowed IP ranges field doesn’t support IPv6 CIDR ranges

[lucaswerkmeister]

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The Allowed IP Ranges field when creating a token (see https://docs.npmjs.com/creating-and-viewing-access-tokens) doesn’t support IPv6 CIDR ranges. This means that, if I’m publishing from an IPv6-enabled environment, I effectively can’t use allowed IP ranges at all, because it doesn’t seem to be possible to force npm publish to use IPv4 only.

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[healer0805]

Yeah, this is a real foot-gun.

The docs say "CIDR notation" for Allowed IP Ranges, but in practice the token UI/validator doesn't accept IPv6 CIDRs, so anyone publishing from an IPv6-first network basically has to leave the feature unused. That's a security regression, not just a missing nicety.

A couple practical ways to sort it out today (none are perfect):

• "Force Node to prefer IPv4 DNS results for the npm CLI process" by setting NODE_OPTIONS=--dns-result-order=ipv4first in the environment running npm publish. This is a known Node-level knob used to steer IPv4/IPv6 preference.
  "Caveat:" depending on OS/network and how the endpoint is resolved, it may not be 100% deterministic (there are open Node discussions around this behavior).

• "Pin publishing to a known IPv4 egress" (CI runner / build agent / NATed environment). It's boring, but it's the only option that's truly predictable if the token is locked to IPv4 ranges.

• "Use npm's local-address config" to bind outbound connections to a specific local interface IP (useful if your box has both v4 and v6 and you can bind to the v4 interface).

What I'd love to see on npm's side:

• Either "accept IPv6 CIDR" in Allowed IP Ranges (best outcome), or
• Add a clear note in docs/UI that the allowlist is IPv4-only right now, and
• Optionally provide an npm setting to "prefer IPv4 for registry connections" so users don't have to rely on Node DNS behavior.

Right now the painful part is exactly what you said: if the model picks IPv6 for the publish path, your IP allowlist becomes "security theater."

[mecodeatlas]

Thanks for taking the time to report this and for the detailed context, @lucaswerkmeister!

We’ve shared this with the npm team for visibility. This is a known limitation that’s already on the team’s radar and is being tracked as a potential improvement, but there isn’t an estimated timeline to share at this time.

Really appreciate you calling this out!