Skip to content
Patch Next
Sign inAdd to your agent

← Actionable
Medium, CVSS 5.3amended

Nodemailer: Quoted local-part can produce malformed envelope recipient through RFC 5322 comment parsing

CVE-2026-100699GHSA-g57g-f23g-4646

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (nodemailer 10.0.9), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

Add to your agent

Affected packages

  • npm nodemailer

    Affected
    >= 9.1.0, < 10.0.9
    Fixed in
    10.0.9

Sources

Severity and exploitation
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-2026-100699: 0.23% estimated exploitation activity in the next 30 days; percentile 14.32 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Nodemailer's 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. For example: is parsed as: The resulting address therefore contains additional attacker-controlled domain text separated by a literal space. The parsed .address value is subsequently propagated into the SMTP envelope: The envelope construction uses the parsed address without another strict address validation step. This 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. Reproduction Input: Observed parser output: A second example: produces: For comparison, the corresponding unquoted form: takes a different code path and is handled by the existing protection differently. Technical Details The issue is caused by different parsing behavior for quoted and unquoted local-parts. The quoted-local-part…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-g57g-f23g-4646

  2. Revision 2 · amended ·

    Amended from osv record GHSA-g57g-f23g-4646

  3. Revision 1 · created ·

    Published from ghsa record GHSA-g57g-f23g-4646

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-100699

Advisory: Nodemailer: Quoted local-part can produce malformed envelope recipient through RFC 5322 comment parsing
IDs: CVE-2026-100699, GHSA-g57g-f23g-4646
Record: https://patchnext.com/advisories/ghsa-g57g-f23g-4646 (revision 3, source checked 26 Oct 2026, 13:06 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 10.0.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm nodemailer: affected >= 9.1.0, < 10.0.9; fixed in 10.0.9

## 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-g57g-f23g-4646 (GitHub-reviewed advisory GHSA-g57g-f23g-4646 lists affected ranges: npm nodemailer >=9.1.0 <10.0.9)
- Verified: https://osv.dev/vulnerability/GHSA-g57g-f23g-4646 (OSV record GHSA-g57g-f23g-4646 lists affected ranges: npm nodemailer >=9.1.0 <10.0.9 (fixed))

Commands are suggestions: review each one before running it.

Loading voting…