Nodemailer: IDN/Punycode domain allow-list bypass 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-2026-92598: 0.40% estimated exploitation activity in the next 30 days; percentile 33.79 (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 resolves an international (IDN / non-ASCII) recipient domain to a different Punycode xn-- label than every UTS‑46‑conformant parser (web browsers, the WHATWG URL Standard, Node's url.domainToASCII, Python's idna). Its address normalizer (normalizeAddress in lib/mime-node/index.js) uses the bundled raw RFC‑3492 Punycode codec with no UTS‑46 mapping/normalization, so a domain that a standards‑compliant validator maps to a trusted domain is delivered by Nodemailer to a different, attacker‑registrable domain. An application that applies a domain allow‑list / same‑domain check to a recipient using a normal IDN‑aware parser (or that shows the normalized recipient to a user for confirmation) and then relies on Nodemailer to deliver to that domain can be induced to send email to an unintended external domain. This is the same weakness class as CVE‑2025‑13033 (Interpretation Conflict, CWE‑436) but reached through IDN/Punycode rather than quoted local‑parts, and it is not…

Published by the source

8 Sep 2026, 21:33 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-wmmp-3585-3rmp

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-wmmp-3585-3rmp

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-wmmp-3585-3rmp

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# Patch Next advisory brief: CVE-2026-92598

Advisory: Nodemailer: IDN/Punycode domain allow-list bypass leads to email delivery to an attacker-controlled domain
IDs: CVE-2026-92598, GHSA-wmmp-3585-3rmp
Record: https://patchnext.com/advisories/ghsa-wmmp-3585-3rmp (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 < 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-wmmp-3585-3rmp (GitHub-reviewed advisory GHSA-wmmp-3585-3rmp lists affected ranges: npm nodemailer >=0 <9.1.0)
- Verified: https://osv.dev/vulnerability/GHSA-wmmp-3585-3rmp (OSV record GHSA-wmmp-3585-3rmp lists affected ranges: npm nodemailer >=0 <9.1.0 (fixed))

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