GHSA-268h-hp4c-crq3

### Summary Nodemailer constructs `List-*` headers from the caller-provided `list` message option using internally prepared header values. The `list.*.comment` field is inserted into those prepared values without removing CR (`\r`) or LF (`\n`) characters. Because prepared headers bypass the normal header-value sanitizer and are passed to `mimeFuncs.foldLines()`, a CRLF sequence in a list comment is emitted as an actual header boundary in the generated RFC822 message. An application that lets a lower-privileged or unauthenticated user influence `list.help.comment`, `list.unsubscribe.comment`, `list.subscribe.comment`, `list.post.comment`, `list.owner.comment`, `list.archive.comment`, or `list.id.comment` can therefore be made to generate messages containing attacker-chosen additional headers. ### Details Source-to-sink evidence: - `lib/mailer/mail-message.js:241-249` calls `_getListHeaders(this.data.list)` and adds each returned value with `this.message.addHeader(listHeader.key, value)`. - `lib/mailer/mail-message.js:253-296` builds each list header value as `{ prepared: true, foldLines: true, value: ... }`. - For `List-ID`, `lib/mailer/mail-message.js:272-279` copies `value.comment` into the generated header value. If `mimeFuncs.isPlainText(comment)` returns true, it wraps the comment in quotes rather than encoding or CRLF-normalizing it. - For the other `List-*` headers, `lib/mailer/mail-message.js:283-288` copies `value.comment` into `(<comment>)`. If `mimeFuncs.isPlainText(comment)` returns true, the value is not encoded or CRLF-normalized. - `lib/mime-node/index.js:323-351` accepts the prepared header object. - `lib/mime-node/index.js:533-540` trusts `options.prepared`; when `foldLines` is set, it pushes `mimeFuncs.foldLines(key + ': ' + value)` directly into the header block. - The normal header-value sanitizer path is bypassed because the value is marked prepared. By contrast, ordinary unprepared header values are normalized in the regular header-building