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.

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00254.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
nodemailer nodemailer unaffected
Version Status Constraints
3.0.0 affected < 10.0.10
10.0.10 unaffected —

No data.

No data.

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Project Subscriptions

Vendors Products
Nodemailer Subscribe
Nodemailer Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/nodemailer/nodemailer/security/advisories/GHSA-39m8-27wv-hr27 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-110871 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-110871 cve-icon
https://www.vulncheck.com/advisories/nodemailer-3.0.0-before-10.0.10-quadratic-dkim-header-unfolding-denial-of-service cve-icon cve-icon cve-icon
History

Thu, 15 Oct 2026 13:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-1322
References
Metrics threat_severity

None

 threat_severity

Moderate

Wed, 14 Oct 2026 23:00:00 +0000

Type Values Removed Values Added
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.
Title Nodemailer 3.0.0 before 10.0.10 Quadratic DKIM Header Unfolding Denial of Service
First Time appeared Nodemailer
Nodemailer nodemailer
Weaknesses CWE-400
CPEs cpe:2.3:a:nodemailer:nodemailer:*:*:*:*:*:*:*:*
Vendors & Products Nodemailer
Nodemailer nodemailer
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-14T22:52:59.681Z

Reserved: 2026-10-14T22:21:21.397Z

Link: CVE-2026-110871

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-14T23:17:28.953

Modified: 2026-10-15T20:33:06.527

Link: CVE-2026-110871

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-10-14T22:52:59Z

Links: CVE-2026-110871 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-15T13:00:18Z

Weaknesses