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.

HighVendor CVSS 7.4 / 10 1 CVE Published Oct 25, 2026 at 1:01 AM UTC

Summary

Mariner

Release Notes

Oct 25, 2026 at 1:01 AM UTC
Published by Microsoft Security Response Center
The publication date reported by the vendor.
Oct 26, 2026 at 2:50 PM UTC
Updated by Microsoft Security Response Center
The vendor changed the advisory after it was first published.
Oct 27, 2026 at 9:20 AM UTC
Added to SecurityAlert
We collected the advisory from the official source.
Oct 27, 2026 at 9:40 PM UTC
Confirmed at the source
Our collector saw this advisory during a later source check.

Details collected from Microsoft Security Response Center.

Official bulletin How SecurityAlert builds this record

Your environment

A vendor advisory can tell you what may be affected. It cannot tell you whether that product and version are installed in your environment.

Keep following

Use the vendor-specific RSS feed or set up alerts for a product your team relies on.

Follow this vendor's RSS feed