---
id: CVE-2026-110869
title: >-
  Nodemailer 3.0.0 before 10.0.13 has a regular expression denial of service in
  SMTPConnection._actionEHLO, whose four AUTH mechanism detection regexes
  contain overlapping whitespace sub-patterns that backtrack quadratically
summary: >-
  Nodemailer 3.0.0 before 10.0.13 has a regular expression denial of service in
  SMTPConnection._actionEHLO, whose four AUTH mechanism detection regexes
  contain overlapping whitespace sub-patterns that backtrack quadratically. A
  malicious o…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-1333
published: '2026-10-14'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T23:17:28.673'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-110869'
references:
  - url: >-
      https://github.com/nodemailer/nodemailer/security/advisories/GHSA-4ffr-jq9g-5ffx
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/nodemailer-3.0.0-before-10.0.13-redos-via-smtp-auth-mechanism-detection-regexes
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-15T00:02:07.189Z'
---

## Overview

Nodemailer 3.0.0 before 10.0.13 has a regular expression denial of service in SMTPConnection._actionEHLO, whose four AUTH mechanism detection regexes contain overlapping whitespace sub-patterns that backtrack quadratically. A malicious or man-in-the-middle SMTP server can reply to EHLO with 250-AUTH, a long whitespace run and a non-matching token, blocking the Node.js event loop for tens of seconds to hours before authentication.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.