{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "nodemailer"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "9.1.0"
            },
            {
              "fixed": "10.0.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-20",
      "CWE-436"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-29T23:44:04Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nNodemailer\u0027s address parser can produce an unexpected recipient address when an RFC 5322 comment follows the domain of an address whose local-part is a quoted string.\n\nFor example:\n\n```text\n\"user\"@example.com(x)evil.com\n```\n\nis parsed as:\n\n```text\n{\n  address: \"user@example.com evil.com\",\n  name: \"\"\n}\n```\n\nThe resulting address therefore contains additional attacker-controlled domain text separated by a literal space.\n\nThe parsed `.address` value is subsequently propagated into the SMTP envelope:\n\n```text\nsrc/addressparser/index.ts\n        \u2193\nrecipient.address\n        \u2193\nsrc/mime-node/index.ts\n        \u2193\nenvelope.to\n```\n\nThe envelope construction uses the parsed address without another strict address validation step.\n\nThis appears to be a variant of the RFC 5322 comment parsing issue addressed by GHSA-cc9r-2j5m-2m83, but it follows a different parser path when the local-part is quoted.\n\n## Reproduction\n\nInput:\n\n```text\n\"user\"@example.com(x)evil.com\n```\n\nObserved parser output:\n\n```text\naddress: \"user@example.com evil.com\"\nname: \"\"\n```\n\nA second example:\n\n```text\n\"a\"@b.com(c)d.com(e)f.com\n```\n\nproduces:\n\n```text\naddress: \"a@b.com d.com f.com\"\nname: \"\"\n```\n\nFor comparison, the corresponding unquoted form:\n\n```text\nuser@example.com(x)evil.com\n```\n\ntakes a different code path and is handled by the existing protection differently.\n\n## Technical Details\n\nThe issue is caused by different parsing behavior for quoted and unquoted local-parts.\n\nThe quoted-local-part variant allows the comment-separated trailing domain atoms to remain in the resulting `.address` value.\n\nThat value is then used when constructing the message envelope:\n\n```text\nenvelope.to = recipients.map(to =\u003e to.address as string)\n```\n\nNo additional strict recipient validation is performed at this boundary.\n\n## Security Impact\n\nThe confirmed impact is that attacker-controlled comment content can result in a malformed/ambiguous recipient address being accepted by the parser and propagated into `envelope.to`.\n\nThe reporter did **not confirm successful delivery to an unintended recipient through a real SMTP server using this exact quoted-local-part variant**.\n\nThe remaining question is how real SMTP servers and other Nodemailer transports handle an envelope recipient containing a value such as:\n\n```text\nuser@example.com evil.com\n```\n\nAn end-to-end SMTP test is required to determine whether this parser behavior results in an exploitable delivery or recipient-validation bypass.\n\n## Relationship to GHSA-cc9r-2j5m-2m83\n\nThis report is intended as a potential variant/follow-up to GHSA-cc9r-2j5m-2m83.\n\nThe existing advisory addresses RFC 5322 comment handling in email domains. This report identifies a separate parser path involving quoted local-parts that can preserve additional domain-like content in the normalized address.\n\nPlease evaluate whether this behavior is already covered by the existing fix or represents a remaining parser variant.\n\n## Suggested Fix\n\nThe parser should consistently reject or correctly terminate addresses containing trailing domain atoms after RFC 5322 comments, regardless of whether the local-part is quoted.\n\nIn particular:\n\n```text\n\"user\"@example.com(x)evil.com\n```\n\nshould not result in:\n\n```text\nuser@example.com evil.com\n```\n\nThe envelope-generation layer should also avoid assuming that a parser-produced address is safe for SMTP delivery without appropriate validation.\n\n## Verification Status\n\nConfirmed:\n\n* Parser accepts the quoted-local-part variant.\n* Parser produces an address containing additional attacker-controlled text.\n* The resulting address is propagated into `envelope.to`.\n\nNot confirmed by reporter:\n\n* Successful delivery through a real SMTP server.\n* Delivery to an unintended recipient.\n* Exploitability against a specific downstream SMTP implementation.",
  "id": "GHSA-g57g-f23g-4646",
  "modified": "2026-09-29T23:44:04Z",
  "published": "2026-09-29T23:44:04Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nodemailer/nodemailer/security/advisories/GHSA-g57g-f23g-4646"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodemailer/nodemailer/commit/2f36eb1aa1dd33e312411dc9b888548e14db54ee"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nodemailer/nodemailer"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodemailer/nodemailer/releases/tag/v10.0.9"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Nodemailer: Quoted local-part can produce malformed envelope recipient through RFC 5322 comment parsing"
}