Threat intelligence dashboard
CVE-2026-100699medium

Nodemailer before 10.0.9 Malformed Envelope Recipient via RFC 5322 Comment

Nodemailer is a Node.js email-sending library. In versions >= 9.1.0 and < 10.0.9, the address parser (src/addressparser) mishandles addresses whose local-part is a quoted string and that are followed by RFC 5322 comments, allowing trailing comment-separated domain atoms to be retained in the normalized address. For example, the input "user"@example.com(x)evil.com is parsed to the address value 'user@example.com evil.com', which contains additional attacker-controlled domain text separated by a literal space. This parsed value is used without further strict recipient validation when the message envelope is built (envelope.to in src/mime-node), so a malformed/ambiguous recipient address can be accepted and placed in the SMTP envelope. Whether this results in delivery to an unintended recipient on real SMTP servers has not been confirmed. The issue is a variant of the RFC 5322 comment parsing problem addressed in GHSA-cc9r-2j5m-2m83, affecting the separate quoted-local-part code path. Version 10.0.9 contains a fix.

Risk score

6.9

CVSS 4.0

Vendor
nodemailer
Product
nodemailer
CWE
CWE-20
Published
Sep 26, 2026
Updated
Sep 28, 2026
CISA KEV
Not flagged

Affected products and versions

nodemailer

nodemailer

Version / rangeStatusType
9.1.0 to before 10.0.9affectedsemver
10.0.9unaffectedsemver

Technical metrics

6.9

CVSS 4.0

Severity
medium
Source
VulnCheck
Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

5.3

CVSS 3.1

Severity
medium
Source
VulnCheck
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N