GHSA-8c8m-p3m8-cjg8: Input Validation

Q: Which deployments are exposed?

Deployments using Nodemailer versions 3.0.0 through 10.1.3 are affected. Exposure exists when an application sends attacker-controlled address text through Nodemailer or parses attacker-controlled From or To headers with mailparser.

Q: What does an attacker need to exploit this?

The attacker only needs control over an address value submitted to the application, or over a From or To header in an inbound message that is parsed. They do not need application access, configuration access, or credentials.

Q: Can address-domain validation prevent exploitation?

Not if validation uses a conformant RFC 5322 parser while delivery uses the affected Nodemailer parsing behavior. A value can validate as an address in an allowed domain but be interpreted by Nodemailer as an attacker-controlled recipient.

Q: What should be done if the affected versions are in use?

Update from the affected 3.0.0 through 10.1.3 range to the fixed release, v10.1.4. Until updated, do not rely solely on RFC 5322 parsing to enforce recipient-domain restrictions for attacker-supplied address text.

Published Oct 23, 2026

Updated

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) <evil@evil.com>) <v@victim.com> names v@victim.com with x(y) <evil@evil.com> 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.

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) <evil@evil.com>) <v@victim.com>, 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) <evil@evil.com>) <v@victim.com>")); // [ { address: 'evil@evil.com', name: 'Victim) v@victim.com' } ]

Python's email.headervalueparser.getaddresslist 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) <evil@evil.com>) <v@victim.com>" }) 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 Software

1 affected componentFixes available

npm/nodemailer>=3.0.0<10.1.4

10.1.4

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade npm/nodemailer to a version that resolves this vulnerability.
Fixed in 10.1.4

Event History

Oct 23, 2026

Advisory Published

via GitHub·09:53 PM

Data Sourced

via GitHub·09:53 PM

DescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

Which deployments are exposed?

Deployments using Nodemailer versions 3.0.0 through 10.1.3 are affected. Exposure exists when an application sends attacker-controlled address text through Nodemailer or parses attacker-controlled From or To headers with mailparser.

What does an attacker need to exploit this?

The attacker only needs control over an address value submitted to the application, or over a From or To header in an inbound message that is parsed. They do not need application access, configuration access, or credentials.

Can address-domain validation prevent exploitation?

Not if validation uses a conformant RFC 5322 parser while delivery uses the affected Nodemailer parsing behavior. A value can validate as an address in an allowed domain but be interpreted by Nodemailer as an attacker-controlled recipient.

What should be done if the affected versions are in use?

Update from the affected 3.0.0 through 10.1.3 range to the fixed release, v10.1.4. Until updated, do not rely solely on RFC 5322 parsing to enforce recipient-domain restrictions for attacker-supplied address text.

GHSA-8c8m-p3m8-cjg8: Input Validation

Affected Software

Remediation

Event History

Frequently Asked Questions

Which deployments are exposed?

What does an attacker need to exploit this?

Can address-domain validation prevent exploitation?

What should be done if the affected versions are in use?

Company

Resources

Contact

Frequently Asked Questions

Which deployments are exposed?

What does an attacker need to exploit this?

Can address-domain validation prevent exploitation?

What should be done if the affected versions are in use?