Nodemailer: Recipient-domain validation bypass via RFC 5322 comment mis-parsing leads to email delivery to an attacker-controlled domain

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

EPSS

• CVE-2026-92597: 0.38% estimated exploitation activity in the next 30 days; percentile 32.30 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Nodemailer's email-address parser treats an RFC 5322 comment ( ... ) inside the domain as a point to concatenate the surrounding text, rather than as folding whitespace (CFWS) that terminates the domain. Consequently a recipient address such as user@good-corp.com(x)evil.com is parsed and delivered to good-corp.comevil.com (registrable domain comevil.com, attacker‑controlled), while a conformant RFC 5322 parser terminates the domain at the comment and reads good-corp.com. An application that decides whether it is allowed to email a recipient by parsing/validating the recipient's domain — with a strict RFC 5322 parser (used without inspecting parse defects) or with a naive prefix/substring allow‑list — and then hands the raw address to Nodemailer for delivery, can be induced to send mail to a domain the attacker controls. This is an Interpretation Conflict (CWE‑436), the same class as CVE‑2025‑13033, reached through the RFC 5322 comment construct (the "Comments" technique in…

Published by the source

8 Sep 2026, 21:32 UTC

Last modified by the source

17 Sep 2026, 11:56 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-cc9r-2j5m-2m83

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-cc9r-2j5m-2m83

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-cc9r-2j5m-2m83

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# Patch Next advisory brief: CVE-2026-92597

Advisory: Nodemailer: Recipient-domain validation bypass via RFC 5322 comment mis-parsing leads to email delivery to an attacker-controlled domain
IDs: CVE-2026-92597, GHSA-cc9r-2j5m-2m83
Record: https://patchnext.com/advisories/ghsa-cc9r-2j5m-2m83 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nodemailer 9.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm nodemailer: affected >= 6.9.16, < 9.1.0; fixed in 9.1.0

## Suggested inspection (read-only)
- `npm ls nodemailer --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on nodemailer.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cc9r-2j5m-2m83 (GitHub-reviewed advisory GHSA-cc9r-2j5m-2m83 lists affected ranges: npm nodemailer >=6.9.16 <9.1.0)
- Verified: https://osv.dev/vulnerability/GHSA-cc9r-2j5m-2m83 (OSV record GHSA-cc9r-2j5m-2m83 lists affected ranges: npm nodemailer >=6.9.16 <9.1.0 (fixed))

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