Nodemailer has SMTP command injection due to unsanitized envelope.size parameter

Exploitation

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

CVSS 4.0

2.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-82854: 1.98% estimated exploitation activity in the next 30 days; percentile 80.51 (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 When a custom envelope object is passed to sendMail() with a size property containing CRLF characters (\r\n), the value is concatenated directly into the SMTP MAIL FROM command without sanitization. This allows injection of arbitrary SMTP commands, including RCPT TO — silently adding attacker-controlled recipients to outgoing emails. Details In lib/smtp-connection/index.js (lines 1161-1162), the envelope.size value is concatenated into the SMTP MAIL FROM command without any CRLF sanitization: This contrasts with other envelope parameters in the same function that ARE properly sanitized: - Addresses (from, to): validated for [\r\n<] at lines 1107-1127 - DSN parameters (dsn.ret, dsn.envid, dsn.orcpt): encoded via encodeXText() at lines 1167-1183 The size property reaches this code path through MimeNode.setEnvelope() in lib/mime-node/index.js (lines 854-858), which copies all non-standard envelope properties verbatim: Since sendCommand() writes the command string followed by…

Published by the source

26 Mar 2026, 22:26 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:47 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-c7w3-x93f-qmm8

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-c7w3-x93f-qmm8

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# Patch Next advisory brief: CVE-2026-82854

Advisory: Nodemailer has SMTP command injection due to unsanitized `envelope.size` parameter
IDs: CVE-2026-82854, GHSA-c7w3-x93f-qmm8
Record: https://patchnext.com/advisories/cve-2026-82854 (revision 3, source checked 26 Oct 2026, 12:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nodemailer 8.0.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm nodemailer: affected < 8.0.4; fixed in 8.0.4

## 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://osv.dev/vulnerability/GHSA-c7w3-x93f-qmm8 (OSV record GHSA-c7w3-x93f-qmm8 lists affected ranges: npm nodemailer >=0 <8.0.4 (fixed))
- Verified: https://github.com/advisories/GHSA-c7w3-x93f-qmm8 (GitHub-reviewed advisory GHSA-c7w3-x93f-qmm8 lists affected ranges: npm nodemailer >=0 <8.0.4)

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