Vulnerability in Nodemailer
CVE-2026-110869
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.
Vulnerability class: ReDoS (Regular Expression Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/nodemailer/nodemailer/security/advisories/GHSA-4ffr-jq9g-5ffx (vendor-advisory)
- www.vulncheck.com/advisories/nodemailer-3.0.0-before-10.0.13-redos-via-smtp-aut… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-110869?
- CVE-2026-110869 is a high-severity vulnerability in Nodemailer, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-10-14.
- How severe is CVE-2026-110869?
- High severity. CVSS v3 base score is 7.5 out of 10.