CVE-2026-100701 Nodemailer 5.0.0 through 10.0.1 TLS servername Cache Confusion
An attacker can exploit a DNS cache flaw in Nodemailer to force incorrect TLS servername validation, potentially disclosing SMTP credentials in multi-tenant environments.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-100701?
CVE-2026-100701 is a medium-severity vulnerability in nodemailer, published on 26 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Nodemailer versions 5.0.0 through 10.0.1 use a process-global DNS cache that is keyed only by the DNS host, while each cache entry also stores the caller-specific TLS servername. When two direct TLS/SMTPS transports (secure: true) resolve the same non-IP host with different tls.servername values, the first transport's servername is returned on the cache hit and overwrites the second transport's explicitly configured value, so Nodemailer sends the wrong SNI value and validates the peer certificate against the wrong identity. In multi-tenant services or SNI-routed SMTP gateways, an attacker who can prime the cache can cause a victim transport to connect to the attacker's TLS virtual host and accept the attacker's certificate even with rejectUnauthorized: true, disclosing the victim's SMTP credentials. Fixed in 10.0.2.
Weakness: CWE-295
Which versions are affected by CVE-2026-100701?
2 open source packages ship an affected version, including nodemailer.
| Package | Affected | Fixed in |
|---|---|---|
nodemailer npm | From 5.0.0 | 10.0.2 |
nodemailer npm | From 5.0.0 | 10.0.2 |
How do I fix CVE-2026-100701?
Upgrade nodemailer to 10.0.2 or later.
Is CVE-2026-100701 being exploited?
There is no known exploitation of CVE-2026-100701 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-HG25385, CLEANSTART-2026-HM32228, CLEANSTART-2026-RE54835, CLSA-2026-1790673224, CLSA-2026-1790676821, CLSA-2026-1792139197 and 21 more.