What’s Vulnerable › Vulnerabilities

CVE-2026-100701: Nodemailer 5.0.0 through 10.0.1 TLS servername Cache Confusion

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-26 · updated 2026-09-30
• Weakness: CWE-295

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.

Affected products

• nodemailer: from 5.0.0 before 10.0.2 — fixed in 10.0.2

How to fix

Upgrade to a fixed version: nodemailer 10.0.2. Check the vendor advisory for mitigations.

References

• https://github.com/nodemailer/nodemailer/security/advisories/GHSA-6vj9-mwq6-2f5v
• https://www.vulncheck.com/advisories/nodemailer-5.0.0-through-10.0.1-tls-servername-cache-confusion

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