What is CVE-2021-23400?

CVE-2021-23400 is a medium-severity vulnerability in Nodemailer, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 6.3/10. Published 2021-06-29.

How severe is CVE-2021-23400?

Medium severity. CVSS v3 base score is 6.3 out of 10.

Vulnerability in Nodemailer

CVE-2021-23400

The package nodemailer before 6.6.1 are vulnerable to HTTP Header Injection if unsanitized user input that may contain newlines and carriage returns is passed into an address object.

Published 2021-06-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.014 (71.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 71st percentile — 71.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.014 · change: 0.000

Affected products

Nodemailer
Nodemailer — versions unspecified

Weakness classification (CWE)

CWE-74 — Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection)

References

snyk.io/vuln/SNYK-JS-NODEMAILER-1296415 (Exploit, Patch, Third Party Advisory)
snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1314737 (Exploit, Patch, Third Party Advisory)
github.com/nodemailer/nodemailer/issues/1289 (Third Party Advisory)
github.com/nodemailer/nodemailer/commit/7e02648cc8cd863f5085bad3cd09087bccf84b9f (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-23400?: CVE-2021-23400 is a medium-severity vulnerability in Nodemailer, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 6.3/10. Published 2021-06-29.
How severe is CVE-2021-23400?: Medium severity. CVSS v3 base score is 6.3 out of 10.