CVE-2026-92597

Nodemailer versions >= 6.9.16 and < 9.1.0 mis-parse RFC 5322 comments in email addresses: in lib/addressparser, a comment closed immediately before a non-break character causes the tokenizer to concatenate the atoms surrounding the comment instead of treating the comment as folding whitespace that terminates the domain. A recipient address such as user@good-corp.com(x)evil.com is therefore read by Nodemailer as the single domain good-corp.comevil.com (registrable domain comevil.com, which an attacker can register) and used for both the SMTP envelope (RCPT TO) and the emitted To:/From: headers, while a conformant RFC 5322 parser terminates the domain at the comment and reads good-corp.com. An application that validates the recipient domain with a strict RFC 5322 parser (without inspecting parse defects) or a naive prefix/substring allow-list and then hands the raw address to Nodemailer can be induced to deliver mail to a domain the attacker controls. Fixed in 9.1.0.

• https://github.com/nodemailer/nodemailer/commit/902b63e
• https://github.com/nodemailer/nodemailer/security/advisories/GHSA-cc9r-2j5m-2m83
• https://www.vulncheck.com/advisories/nodemailer-before-9.1.0-email-domain-validation-bypass-via-rfc-5322-comment