CVE-2026-100700

Nodemailer resolves an international (IDN / non-ASCII) recipient domain to a different Punycode label than every UTS-46-conformant parser (web browsers, WHATWG URL Standard, Node's url.domainToASCII, Python's idna). Its address normalizer (_normalizeAddress) may lead to incorrect domain resolution, enabling phishing or message misdirection.

Nodemailer's process-global DNS cache is keyed only by `host`, but each cache entry also stores the caller-specific TLS `servername`. When two direct SMTPS transports use the same DNS host with different `tls.servername` values, the first transport's server name is returned to the second.

Nodemailer's address parser parses comma-separated addresses in quadratic time (O(n²)) in the number of addresses. A single crafted address string (e.g., To, Cc, Bcc, From, Reply-To) can cause significant slowdown.

Nodemailer's email-address parser treats an RFC 5322 comment inside the domain as a point to concatenate the surrounding text, rather than as folding whitespace (CFWS) that terminates the domain. This can lead to incorrect parsing, e.g., [email protected](x)evil.c..., potentially redirecting messages or bypassing validation.

A vulnerability in the Nodemailer library allows header injection via the `list.*.comment` field, which is not sanitized for CR (`\r`) and LF (`\n`) characters. An attacker can supply a malicious value in this field, leading to email header spoofing.

Nodemailer's disableFileAccess/disableUrlAccess options are a security sandbox that forbids untrusted message content from reading local files or making outbound HTTP(S) requests. The fix for GHSA-wqvq-jvpq-h66f may be incomplete, allowing bypass of the sandbox.

A vulnerability in Nodemailer allows bypassing the `disableFileAccess` and `disableUrlAccess` options when using `jsonTransport`. While the normal MIME streaming path enforces these restrictions, `jsonTransport` serializes the message in a way that bypasses them, potentially enabling access to local files or external URLs.

In nodemailer v9.0.0, the message-level `raw` option bypasses `disableFileAccess` and `disableUrlAccess` protections, enabling arbitrary file reads and full SSRF (Server-Side Request Forgery) in the sent message.

Nodemailer disables TLS certificate verification in its internal HTTPS fetch client by setting rejectUnauthorized: false in lib/fetch/index.js. This causes OAuth2 token requests to trust invalid or self-signed HTTPS certificates.

Nodemailer before 8.0.4 is vulnerable to SMTP command injection through the unsanitized envelope.size parameter. When an application passes a custom envelope object with a size property containing CRLF characters to sendMail(), the value is concatenated into the SMTP MAIL FROM command (as SIZE=...) without sanitization, allowing injection of arbitrary SMTP commands such as RCPT TO to silently add attacker-controlled recipients.