Nodemailer: RFC 5322 comment inside an angle-bracket address is never stripped

{
  "id": "d21fa5de22665263540eb62a363be0aac95a31c8e2add9a88f4e215c723077c3",
  "url": "https://osv.dev/vulnerability/GHSA-g73g-hqqh-jr95",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Nodemailer: RFC 5322 comment inside an angle-bracket address is never stripped",
    "summary": "## Summary Nodemailer's address parser has three published, patched fixes for RFC 5322 comment `( ... )` handling inside an addr-spec: GHSA-cc9r-2j5m-2m83 (comment glued two domain atoms into one), GHSA-g57g-f23g-4646 (the same glue for a quoted local part), and the related ReDoS fixes GHSA-prgh-xp8r-p3m5 / GHSA-v53p-9fqp-m79j. All three fixes live in `_handleAddress()`'s `joins` / `_recoverAddrSpec()` logic in `src/addressparser/index.ts`, and that logic is exercised whenever the local text-accumulation path in the tokenizer runs. That logic is **never reached at all** for the single most common way a recipient is written: a display name followed by an angle-bracket address, `Name `. When the input inside the angle brackets itself contains an RFC 5322 comment, e.g. ``` Legit User ``` the comment is not recognized as an operator, is not stripped, and the parenthesis characters survive **verbatim** inside the parsed address. That value is used as-is for `envelope.to` and is written raw onto the wire in the `RCPT TO` SMTP command. I confirmed this end to end: * against nodemailer's own `jsonTransport`/`streamTransport` (`envelope.to` and the emitted `To:` header both carry the malformed value), and * against a real SMTP server (`aiosmtpd`), where the malformed value is fatal to the transaction (`501 Syntax: RCPT TO: [SP ]`, all recipients rejected). This reproduces unmodified on every version I tested from `6.9.16` through the current `10.0.12` HEAD, i.e. it predates and surviv",
    "evidence": "osv:GHSA-g73g-hqqh-jr95",
    "products": [
      {
        "name": {
          "value": "nodemailer",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "10.0.13",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "GHSA-g73g-hqqh-jr95",
      "aliases": [
        "CVE-2026-110870",
        "GHSA-g73g-hqqh-jr95"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "3.0.0"
                },
                {
                  "fixed": "10.0.13"
                }
              ]
            }
          ],
          "package": {
            "name": "nodemailer",
            "purl": "pkg:npm/nodemailer",
            "ecosystem": "npm"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-g73g-hqqh-jr95/GHSA-g73g-hqqh-jr95.json",
            "last_known_affected_version_range": "<= 10.0.12"
          }
        }
      ],
      "modified": "2026-10-27T15:15:07.723338698Z",
      "provider": "osv",
      "references": [
        "https://github.com/nodemailer/nodemailer/security/advisories/GHSA-g73g-hqqh-jr95",
        "https://github.com/nodemailer/nodemailer/commit/a502247555fd81773eac337486781f3b6008e16a",
        "https://github.com/nodemailer/nodemailer",
        "https://github.com/nodemailer/nodemailer/releases/tag/v10.0.13"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-20",
          "CWE-436"
        ],
        "severity": "MODERATE",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-27T15:04:36Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-110870",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 462819,
  "published_at": "2026-10-27T15:04:36+00:00"
}