---
title: "CVE-2026-110869: Nodemailer - Denial of Service"
description: "Nodemailer < 10.0.13 contains a regular expression denial of service caused by overlapping whitespace sub-patterns in SMTPConnection._actionEHLO AUTH mechanism detection regexes, letting a malicious or man-in-the-middle SMTP server block the Node.js event loop, exploit requires interaction with a malicious SMTP server."
url: https://panop.io/threat-heartbeat/CVE-2026-110869/
---

# CVE-2026-110869 Nodemailer - Denial of Service

Nodemailer < 10.0.13 contains a regular expression denial of service caused by overlapping whitespace sub-patterns in SMTPConnection.\_actionEHLO AUTH mechanism detection regexes, letting a malicious or man-in-the-middle SMTP server block the Node.js event loop, exploit requires interaction with a malicious SMTP server.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-110869)

## Details

Type

Denial of Service

Impact

Denial Of Service, Man In The Middle

CVSS vector

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

Published

14 October 2026

Updated

15 October 2026

Weakness

[CWE-1333](https://cwe.mitre.org/data/definitions/1333.html)

## Vendor fix

Update to version 10.0.13 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-110869](https://nvd.nist.gov/vuln/detail/CVE-2026-110869)
- [https://github.com/nodemailer/nodemailer/security/advisories/GHSA-4ffr-jq9g-5ffx](https://github.com/nodemailer/nodemailer/security/advisories/GHSA-4ffr-jq9g-5ffx)
- [https://www.vulncheck.com/advisories/nodemailer-3.0.0-before-10.0.13-redos-via-smtp-auth-mechanism-detection-regexes](https://www.vulncheck.com/advisories/nodemailer-3.0.0-before-10.0.13-redos-via-smtp-auth-mechanism-detection-regexes)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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