ip-address: no classifier recognizes the NAT64 local-use range 64:ff9b:1::/48, allowing SSRF and trust-boundary bypass

ip-address is a library for parsing and manipulating IPv4 and IPv6 addresses in JavaScript. From 10.2.0 until 10.5.1, the Address6 isPrivate classifier in src/ipv6.ts does not recognize the NAT64 local-use range 64:ff9b:1::/48. Applications that combine isPrivate, isLoopback, and isLinkLocal for a trust-boundary decision can treat an internal IPv4 destination encoded through that range as external. Exploitation depends on a server network using an operator-selected NAT64 prefix within the local-use range. A successful bypass can cross the intended network trust boundary. This issue is fixed in version 10.5.1.

Source published

28 Sep 2026 17:45:27 UTC

Source modified

28 Sep 2026 18:12:34 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 6.9 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:H/SI:N/SA:N