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

Exploitation

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

CVSS

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

EPSS

• CVE-2026-110870: 0.27% estimated exploitation activity in the next 30 days; percentile 18.83 (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 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…

Published by the source

27 Oct 2026, 15:04 UTC

Last modified by the source

27 Oct 2026, 15:15 UTC

Source last checked

28 Oct 2026, 06:00 UTC

1. Revision 2 · amended · 28 Oct 2026

   Amended from osv record GHSA-g73g-hqqh-jr95

2. Revision 1 · created · 27 Oct 2026

   Published from ghsa record GHSA-g73g-hqqh-jr95

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# Patch Next advisory brief: CVE-2026-110870

Advisory: Nodemailer: RFC 5322 comment inside an angle-bracket address is never stripped
IDs: CVE-2026-110870, GHSA-g73g-hqqh-jr95
Record: https://patchnext.com/advisories/ghsa-g73g-hqqh-jr95 (revision 2, source checked 28 Oct 2026, 06:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nodemailer 10.0.13. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm nodemailer: affected >= 3.0.0, < 10.0.13; fixed in 10.0.13

## 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-g73g-hqqh-jr95 (GitHub-reviewed advisory GHSA-g73g-hqqh-jr95 lists affected ranges: npm nodemailer >=3.0.0 <=10.0.12)
- Verified: https://osv.dev/vulnerability/GHSA-g73g-hqqh-jr95 (OSV record GHSA-g73g-hqqh-jr95 lists affected ranges: npm nodemailer >=3.0.0 <10.0.13 (fixed))

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