Summary
Nodemailer: A nested comment ends early in addressparser, releasing the rest of the comment as a recipient
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) <[email protected]>) <[email protected]> names [email protected] with x(y) <[email protected]> as a comment, and Nodemailer read it as the address [email protected]. 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) <[email protected]>) <[email protected]>, which validates as [email protected]. Nodemailer delivers to [email protected]. 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
const addressparser = require('nodemailer/lib/addressparser');
console.log(addressparser("Victim (x(y) <[email protected]>) <[email protected]>"));
// [ { address: '[email protected]', name: 'Victim) [email protected]' } ]
Python's email._header_value_parser.get_address_list reads the same value as [email protected] 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) <[email protected]>) <[email protected]>" }) 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.
Impact
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
GHSA-8C8M-P3M8-CJG8 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (10.1.4); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is GHSA-8C8M-P3M8-CJG8? GHSA-8C8M-P3M8-CJG8 is a medium-severity improper input validation vulnerability in nodemailer (npm), affecting versions >= 3.0.0, < 10.1.4. It is fixed in 10.1.4. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is GHSA-8C8M-P3M8-CJG8? GHSA-8C8M-P3M8-CJG8 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of nodemailer are affected by GHSA-8C8M-P3M8-CJG8? nodemailer (npm) versions >= 3.0.0, < 10.1.4 is affected.
- Is there a fix for GHSA-8C8M-P3M8-CJG8? Yes. GHSA-8C8M-P3M8-CJG8 is fixed in 10.1.4. Upgrade to this version or later.
- Is GHSA-8C8M-P3M8-CJG8 exploitable, and should I be worried? Whether GHSA-8C8M-P3M8-CJG8 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-8C8M-P3M8-CJG8 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-8C8M-P3M8-CJG8? Upgrade
nodemailerto 10.1.4 or later.