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Response snapshot Oct 26, 2026, 23:11 UTC

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VulnerabilityGHSA-8c8m-p3m8-cjg8

Nodemailer: A nested comment ends early in addressparser, releasing the rest of the comment as a recipient

RFC 5322 comments nest. addressparser ended a comment at the first `)`, including the one that closes a nested comment, and parsed the rest of the outer comment as header text. `Victim (x(y) ) ` names `v@victim.com` with `x(y) ` as a comment, and Nodemailer read it as the address `evil@evil.com`.

Published Updated

At a glance

Exploited
Not known
Severity
Not scored yet
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: nodemailer: 10.1.4. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-8c8m-p3m8-cjg8 (opens a new tab)

What happened

### Vulnerability summary

RFC 5322 comments nest. addressparser ended a comment at the first `)`, including the one that closes a nested comment, and parsed the rest of the outer comment as header text. `Victim (x(y) ) ` names `v@victim.com` with `x(y) ` as a comment, and Nodemailer read it as the address `evil@evil.com`. This is the same shape as the escaped parenthesis fixed in 10.1.2, reached through nesting instead of a quoted-pair. Affected: 3.0.0 through 10.1.3.

### Attacker capabilities

The attacker controls the text of an address that an application passes to Nodemailer, or the From or To 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.

Continue reading

### Realistic exploitation scenario

An application validates a submitted address with a conformant parser and allows only its own domain. The attacker submits `Victim (x(y) ) `, which validates as `v@victim.com`. Nodemailer delivers to `evil@evil.com`.

In the inbound direction, a DMARC or display layer built on a conformant parser and a mail client built on mailparser disagree on the author of the same message, which is the setting for sender spoofing. The boundary crossed is the application's recipient allow list, or the author check of the receiving side.

### Proof of concept

```js const addressparser = require('nodemailer/lib/addressparser'); console.log(addressparser("Victim (x(y) ) ")); // [ { address: 'evil@evil.com', name: 'Victim) v@victim.com' } ] ```

Python's `email._header_value_parser.get_address_list` reads the same value as `v@victim.com` with the display name `Victim`, with no defects reported.

The envelope a message gets is built from the same parse, so `sendMail({ to: "Victim (x(y) ) " })` issues the RCPT TO shown above.

### Security impact

Mail intended for an approved recipient is delivered to an attacker chosen domain, disclosing its content, and parsers built on this module report a different author than conformant ones. The misreading only occurs on values a conformant validator approves, so correct validation is bypassed. Affected are applications that pass user influenced addresses to Nodemailer and consumers of the standalone parser such as mailparser.

The fix counts comment depth and ends a comment only at the `)` that closes the outermost one.

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

Affected package ranges reported by GitHub: nodemailer: >= 3.0.0, < 10.1.4

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-8c8m-p3m8-cjg8 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-8c8m-p3m8-cjg8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). Nodemailer: A nested comment ends early in addressparser, releasing the rest of the comment as a recipient. https://kevwire.com/record/GHSA-8c8m-p3m8-cjg8

MLA

"Nodemailer: A nested comment ends early in addressparser, releasing the rest of the comment as a recipient." KEVWire, 23 Oct. 2026, kevwire.com/record/GHSA-8c8m-p3m8-cjg8.

Chicago

KEVWire. "Nodemailer: A nested comment ends early in addressparser, releasing the rest of the comment as a recipient." Last modified October 23, 2026. https://kevwire.com/record/GHSA-8c8m-p3m8-cjg8.

Evidence summary (plain text)

Nodemailer: A nested comment ends early in addressparser, releasing the rest of the comment as a recipient (Oct 23, 2026).
RFC 5322 comments nest. addressparser ended a comment at the first `)`, including the one that closes a nested comment, and parsed the rest of the outer comment as header text. `Victim (x(y) ) ` names `v@victim.com` with `x(y) ` as a comment, and Nodemailer read it as the address `evil@evil.com`. This is the same shape as the escaped parenthesis fixed in 10.1.2, reached through nesting instead of a quoted-pair. Affected: 3.0.0 through 10.1.3.

The attacker controls the text of an address that an application passes to Nodemailer, or the From or To 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.
Sources:
GitHub-reviewed advisory GHSA-8c8m-p3m8-cjg8: https://github.com/advisories/GHSA-8c8m-p3m8-cjg8
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: GHSA-8c8m-p3m8-cjg8.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 20:55 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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