A flaw in Node.js TLS hostname verification can cause a server certificate to be validated against a different IP address than the one the client connected to, when the host is a non-canonical IPv4 literal with a leading zero, such as `0127.0.0.1`.

`tls.checkServerIdentity()` normalizes the host following the WHATWG URL rules, which read a leading-zero octet as octal (`0127.0.0.1` becomes `87.0.0.1`), while the connection is made through the operating system resolver, which on some platforms such as macOS reads it as decimal (`127.0.0.1`). A server at the connected address can then be authenticated with a certificate issued for another IP address.

This vulnerability affects Node.js **26.x**, **24.x**, and **22.x**.

A flaw in Node.js TLS hostname verification can cause a server certificate to be validated against a different IP address than the one the client connected to, when the host is a non-canonical IPv4 literal with a leading zero, such as `0127.0.0.1`.

`tls.checkServerIdentity()` normalizes the host following the WHATWG URL rules, which read a leading-zero octet as octal (`0127.0.0.1` becomes `87.0.0.1`), while the connection is made through the operating system resolver, which on some platforms such as macOS reads it as decimal (`127.0.0.1`). A server at the connected address can then be authenticated with a certificate issued for another IP address.

This vulnerability affects Node.js **26.x**, **24.x**, and **22.x**.

corepack24-24.22.1-1.1 on GA media

Affected: Ubuntu:Pro:14.04:LTS: nodejs, Ubuntu:Pro:16.04:LTS: nodejs, Ubuntu:Pro:18.04:LTS: nodejs, Ubuntu:Pro:20.04:LTS: nodejs, Ubuntu:Pro:22.04:LTS: nodejs, Ubuntu:24.04:LTS: nodejs, Ubuntu:26.10: nodejs, Ubuntu:26.04:LTS: nodejs

[Unknown description]