High · CVSS 7.1CVE-2026-110871

Nodemailer 3.0.0 before 10.0.10 Quadratic DKIM Header Unfolding Denial of ServiceCVE-2026-110871

Answer in brief

CVE-2026-110871 records a High severity (CVSS 7.1) vulnerability in Nodemailer 3.0.0 before 10.0.10 Quadratic DKIM Header Unfolding Denial of Service. The current sources do not mark it as known exploited. The current feed maps nodemailer/nodemailer (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 14, 2026Updated Oct 14, 2026Source checked Oct 15, 2026First seen by HOL Oct 14, 2026Material review Oct 14, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.1
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps nodemailer/nodemailer (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
nodemailer/nodemailergeneric	>=3.0.0 <10.0.10	10.0.10

Recommended response

Check inventory. Check lockfiles and deployed manifests for nodemailer/nodemailer.
Review the reported fix. Update nodemailer/nodemailer to 10.0.10 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 14, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 14, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 14, 2026

Sources and claim methodology

Upstream source description

Nodemailer from 3.0.0 before 10.0.10 contains a denial of service vulnerability in MessageParser.parseHeaders that allows users to exhaust CPU through quadratic header unfolding. Attackers can supply large recipient lists or long headers that fold into tens of thousands of continuation lines, blocking the Node.js event loop during DKIM signing.

Quoted source text, attributed separately from HOL analysis.