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Uncontrolled Resource ConsumptionWeakness · CWE-400

CVE-2026-38728

HIGH · 7.5 CVSS v3.1 Published 2026-05-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An issue in Nodemailer smtp_server before v.3.18.3 allows a remote attacker to cause a denial of service via the SMTPStream._write, lib/smtp-stream.js components

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A denial-of-service vulnerability exists in Nodemailer's smtp_server module prior to version 3.18.3. The vulnerability is located in the SMTPStream._write function within lib/smtp-stream.js, where specially crafted SMTP data from a remote attacker can trigger the DoS condition.

MitigationUpgrade smtp_server to version 3.18.3 or later. If immediate patching is not feasible, implement rate limiting on SMTP connections and restrict network exposure to trusted sources.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify smtp_server installation
    Run 'npm list smtp_server' in your project directory to list the installed smtp_server package and its version
    Affected if smtp_server is not listed in node_modules or returns a version prior to 3.18.3
  2. Verify package.json dependency
    Check your package.json file for the smtp_server dependency entry and compare the version range to the vulnerable versions (< 3.18.3)
    Affected if package.json specifies smtp_server with a version less than 3.18.3
  3. Inspect vulnerable source file
    Locate lib/smtp-stream.js within the smtp_server module directory and verify the SMTPStream._write function exists (this confirms the vulnerable component is present)
    Affected if The file lib/smtp-stream.js exists and contains the SMTPStream._write function
  4. Determine active SMTP server exposure
    Check your application code for instances where smtp_server is imported and the server is started (e.g., Server.listen or similar calls), and verify network exposure of the SMTP port
    Affected if Your application code starts an SMTP server using smtp_server and the port is accessible to untrusted network sources

You are affected if smtp_server version is lower than 3.18.3 and your application runs an SMTP server using the vulnerable module that is accessible to remote attackers sending specially crafted SMTP data.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade smtp_server to version 3.18.3 or later. If immediate patching is not feasible, implement rate limiting on SMTP connections and restrict network exposure to trusted sources.

Recommended fix Moderate confidence

smtp_server v3.18.3 or later

  1. 1. Identify the current version of smtp_server in your project by checking package.json or running `npm list smtp_server`
  2. 2. If using npm, run `npm update smtp_server` to upgrade to the latest version
  3. 3. Alternatively, install the specific fixed version by running: `npm install [email protected]`
  4. 4. Verify the upgrade was successful by running `npm list smtp_server` and confirming the version is 3.18.3 or later
  5. 5. Test your email functionality to ensure the upgrade does not break existing functionality
  6. 6. Rebuild and redeploy your application with the updated dependency

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-38728 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data