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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

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 None

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 0.00305.

Exploitation poc

Automatable yes

Technical Impact partial

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 < 10.0.13
10.0.13 unaffected —

No data.

No data.

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No data.

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-4ffr-jq9g-5ffx cve-icon cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-110869 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-110869 cve-icon
https://www.vulncheck.com/advisories/nodemailer-3.0.0-before-10.0.13-redos-via-smtp-auth-mechanism-detection-regexes cve-icon cve-icon cve-icon
History

Thu, 15 Oct 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

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

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Important

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

Type Values Removed Values Added
Description 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.
Title Nodemailer 3.0.0 before 10.0.13 ReDoS via SMTP AUTH Mechanism Detection Regexes
First Time appeared Nodemailer
Nodemailer nodemailer
Weaknesses CWE-1333
CPEs cpe:2.3:a:nodemailer:nodemailer:*:*:*:*:*:*:*:*
Vendors & Products Nodemailer
Nodemailer nodemailer
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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: 2026-10-15T15:35:29.075Z

Reserved: 2026-10-14T22:21:21.396Z

Link: CVE-2026-110869

cve-icon Vulnrichment

Updated: 2026-10-15T15:35:20.371Z

cve-icon NVD

Status : Received

Published: 2026-10-14T23:17:28.673

Modified: 2026-10-15T16:17:48.013

Link: CVE-2026-110869

cve-icon Redhat

Severity : Important

Publid Date: 2026-10-14T22:52:57Z

Links: CVE-2026-110869 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-15T12:30:04Z

Weaknesses