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.
https://github.com/beaugunderson/ip-address/security/advisories/GHSA-2vr4-cq9g-pvrc
https://github.com/beaugunderson/ip-address/releases/tag/v10.5.1
https://github.com/beaugunderson/ip-address/commit/ab3dc88bcf5374344168a2ba075ca7ac4ff257f8
Published: 2026-09-28
Updated: 2026-09-28
Base Score: 5.2
Vector: CVSS2#AV:L/AC:L/Au:S/C:P/I:N/A:C
Severity: Medium
Base Score: 8.4
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity: High
Base Score: 6.9
Vector: 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
Severity: Medium
EPSS: 0.00386