CVE-2026-121424: Nodemailer address parsing bypass in nested RFC 5322 comments

CVE-2026-121424 · Severity: medium · CVSS 6.5 · Published 2026-11-03

Nodemailer is a widely-used Node.js library for sending emails. A parsing flaw in its address validation allows attackers to craft email addresses that trick the parser into delivering mail to unintended recipients or spoofing sender addresses, bypassing recipient allow lists and validation checks. An attacker can submit specially crafted addresses that hide malicious email targets within RFC 5322 comment syntax, causing mail intended for legitimate recipients to be sent to attacker-controlled addresses instead.

Technologies: Nodemailer. Vendors: Nodemailer.

Quick answers

Is CVE-2026-121424 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-121424 being exploited in the wild.
How severe is CVE-2026-121424?
Medium severity, with a CVSS score of 6.5, published 3 November 2026.
Which products and versions are affected?
Nodemailer 3.0.0 before 10.1.4.
Is there a fix for CVE-2026-121424?
Yes: fixed in 10.1.4. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-121424 attacked?
It is attacked over the network.
Am I affected by CVE-2026-121424?
Check whether you run Nodemailer at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • Fixed in: 10.1.4

Technical details

The addressparser component in Nodemailer incorrectly handles nested RFC 5322 comments by terminating comment parsing at the first closing parenthesis instead of matching nested depth, causing the remainder of an outer comment to be treated as valid header text. An attacker can submit a syntactically valid RFC 5322 address (which passes conformant validators) such as "Victim (x(y) <evil@evil.com>) <v@victim.com>" that a conformant parser reads as v@victim.com but Nodemailer parses as evil@evil.com. This bypasses recipient validation on the application side and enables mail redirection and sender spoofing in inbound parsing scenarios.

Affected products

  • Nodemailer Nodemailer 3.0.0 before 10.1.4

Timeline

  • 2026-10-19: disclosed: Security advisory GHSA-8c8m-p3m8-cjg8 published
  • 2026-10-19: patched: Fixed in version 10.1.4

References

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