Is CVE-2026-38728 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-38728 being exploited in the wild.

How severe is CVE-2026-38728?

High severity, with a CVSS score of 7.5, published 15 May 2026.

Which products and versions are affected?

Nodemailer Smtp-Server < 3.18.3; smtp-server (npm) SEMVER:introduced=0,fixed=3.18.3.

Is there a fix for CVE-2026-38728?

Yes. smtp-server (npm): upgrade to 3.18.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-38728 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-38728?

Check whether you run Nodemailer Smtp-Server or smtp-server (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-38728: Nodemailer smtp-server Denial of Service via memory exhaustion

Q: Is there a fix for CVE-2026-38728?

Yes. smtp-server (npm): upgrade to 3.18.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-38728 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-38728?

Check whether you run Nodemailer Smtp-Server or smtp-server (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-38728 · Severity: high · CVSS 7.5 · Published 2026-05-15

The smtp-server library, used to create custom SMTP email server applications, is vulnerable to a denial-of-service attack. An unauthenticated remote attacker can crash the server or cause it to become unresponsive by sending a continuous stream of data without newline characters. This exhausts the server's memory, potentially disrupting email delivery services and impacting business operations.

Vendors: Nodemailer, npm.

Quick answers

Is CVE-2026-38728 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-38728 being exploited in the wild.
How severe is CVE-2026-38728?: High severity, with a CVSS score of 7.5, published 15 May 2026.
Which products and versions are affected?: Nodemailer Smtp-Server < 3.18.3; smtp-server (npm) SEMVER:introduced=0,fixed=3.18.3.
Is there a fix for CVE-2026-38728?: Yes. smtp-server (npm): upgrade to 3.18.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-38728 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-38728?: Check whether you run Nodemailer Smtp-Server or smtp-server (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

smtp-server (npm): upgrade to 3.18.3 or later
```
npm install smtp-server@3.18.3
```

Technical details

A vulnerability in the `SMTPStream._write` method in `lib/smtp-stream.js` allows for uncontrolled resource consumption. The command parser appends incoming TCP chunks to an internal `_remainder` buffer, which is only cleared upon encountering a newline character. By sending a large volume of data without newlines, a remote unauthenticated attacker can cause this buffer to grow indefinitely. This leads to heap exhaustion, significant garbage collection overhead that freezes the Node.js event loop, and eventual process crashes. The issue is resolved in version 3.18.3.

Affected products

Nodemailer smtp-server < 3.18.3

Identifiers

CVE-2026-38728
GHSA-fv2f-rw9f-v9cm

Timeline

2026-05-15: disclosed
2026-05-15: advisory
2026-05-15: patched: Version 3.18.3 released

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.