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**.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Nodejs | — | Upgrade to the latest version of Node.jsUpgrade Node.js to version 24.22.1Upgrade Node.js to version 26.12.1Upgrade Node.js to version 22.23.4 | Oct 26, 2026 | Oct 23, 2026 |
| Redhat_linux | — | No solution exists | Oct 26, 2026 | Oct 21, 2026 |
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