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Advisory record · GHSA-4g23-2xm8-66gc

Nodemailer: Quadratic (O(n^2)) SMTP client reply parsing lets a malicious server or MITM cause a pre-auth remote denial of service

CVSS 8.2 HighEPSS 0.0036 · 29th percentile

Published by the GitHub Advisory Database at 27 Oct 2026, 15:04 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
nodemailernpm>=3.0.0, <10.0.1010.0.10
Identifiers
GHSA-4g23-2xm8-66gc · CVE-2026-110872
Weakness (CWE)
CWE-400 · CWE-407
Tags
Published
27 Oct 2026
Updated
27 Oct 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Nodemailer versions from 3.0.0 before 10.0.10 are affected. Its SMTP client reassembles multiline server replies in a way that takes quadratic CPU time as a reply grows, so a malicious SMTP server, or an on-path attacker on a plaintext or pre-STARTTLS connection, that streams continuation lines without finishing the reply can block the Node.js event loop before authentication. The source reports that this freezes the whole process for as long as data keeps arriving. Upgrade to nodemailer 10.0.10, which is listed as the fixed version.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
8.2 High 4.0 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N CNA (VulnCheck)
  • CISA KEV Not listed.
  • EPSS 0.0036, the 29th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 13:33 UTC First seen by agentprime
  2. 31 Oct 2026, 13:33 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.