CVE-2026-38728Network attack vector

Unauthenticated service interruption via unbounded command buffer

Published May 15, 2026 · Updated May 15, 2026

Memory exhaustion in Nodemailer smtp-server before 3.18.3 allows remote attackers to hang or crash the SMTP service over the network. The SMTPStream._write method in lib/smtp-stream.js appends newline-free TCP chunks to _remainder and never bounds or clears the buffer until a newline arrives. Any unauthenticated SMTP client can exhaust heap memory, causing prolonged garbage-collection pauses that freeze the event loop or terminate the process.

CVSS severity8.7
High
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory exhaustion in Nodemailer smtp-server before 3.18.3 allows remote attackers to hang or crash the SMTP service over the network. The SMTPStream._write method in lib/smtp-stream.js appends newline-free TCP chunks to _remainder and never bounds or clears the buffer until a newline arrives. Any unauthenticated SMTP client can exhaust heap memory, causing prolonged garbage-collection pauses that freeze the event loop or terminate the process.

The record

CVE
CVE-2026-38728
Published
May 15, 2026
Updated
May 15, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 15, 2026CVE publishedPublication date reported by the CVE source.
  2. May 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.7GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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