CVE-2026-110869 Nodemailer 3.0.0 before 10.0.13 ReDoS via SMTP AUTH Mechanism Detection Regexes
A malicious SMTP server can cause a denial of service in Nodemailer by triggering quadratic backtracking in regexes during EHLO response parsing.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-110869?
CVE-2026-110869 is a high-severity denial of service vulnerability in nodemailer, published on 14 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-1333
Which versions are affected by CVE-2026-110869?
2 open source packages ship an affected version, including nodemailer.
| Package | Affected | Fixed in |
|---|---|---|
nodemailer npm | From 3.0.0 | 10.0.13 |
nodemailer npm | From 3.0.0 | 10.0.13 |
How do I fix CVE-2026-110869?
Upgrade nodemailer to 10.0.13 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-110869 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-110869 exists.
Sources
Also known as DEBIAN-CVE-2026-110869, ECHO-2ec1-76e4-8d52, GHSA-4ffr-jq9g-5ffx, GHSA-mgrc-5q39-2h34, UBUNTU-CVE-2026-110869.