Affected: npm: nodemailer

### 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…