CVE-2026-101910: Beaugunderson IP-Address

Medium severity, CVSS 6.9. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Beaugunderson IP-Address: from 10.2.0, before 10.5.1 (fixed in 10.5.1)

Published 2026-09-28. Last modified 2026-09-30.