CVE-2026-82660

Nodemailer before 8.0.9 fails to enforce disableFileAccess and disableUrlAccess options during message normalization in jsonTransport. Attackers can read local files or fetch URLs by supplying path or href values in message content fields, bypassing intended access controls.

Nodemailer before 8.0.9 fails to enforce disableFileAccess and disableUrlAccess options during message normalization in jsonTransport. Attackers can read local files or fetch URLs by supplying path or href values in message content fields, bypassing intended access controls.

Nodemailer before 8.0.9 fails to enforce disableFileAccess and disableUrlAccess options during message normalization in jsonTransport. Attackers can read local files or fetch URLs by supplying path or href values in message content fields, bypassing intended access controls.

Summary

Nodemailer's disableFileAccess and disableUrlAccess options are intended to prevent message content and attachments from reading local files or fetching URLs. The normal MIME streaming path enforces those options in MimeNode._getStream(). However, jsonTransport serializes messages by calling mail.normalize(), which resolves html, text, alternatives, calendar events, and attachments through shared.resolveContent() before MIME generation. shared.resolveContent() reads local files and fetches HTTP(S) URLs directly, without receiving or checking disableFileAccess or disableUrlAccess.

As a result, applications that use jsonTransport as a safe serializer or queue payload generator while relying on disableFileAccess / disableUrlAccess can still be made to read local files into the generated JSON output or make outbound HTTP requests when an attacker controls message content fields such as attachment path or text.href.

The same missing-enforcement root cause is also reachable before normal streaming when attachDataUrls causes _convertDataImages() to call mail.resolveContent(mail.data, 'html', ...); this should be fixed with the same access-control check.

Details

Source-to-sink evidence:

• lib/nodemailer.js:42-45 selects JSONTransport when createTransport({ jsonTransport: true, ... }) is used.
• lib/mailer/mail-message.js:34-39 copies transport-level disableFileAccess and disableUrlAccess options into mail.data.
• lib/json-transport/index.js:52-76 serializes mail by calling mail.normalize((err, data) => ...).
• lib/mailer/mail-message.js:46-135 implements resolveAll() and calls shared.resolveContent(...args, ...) for html, text, watchHtml, amp, icalEvent, alternatives, and attachments.
• lib/shared/index.js:506-562 implements resolveContent().
• lib/shared/index.js:540-541 fetches HTTP(S) content with nmfetch(content.path || content.href).
• lib/shared/index.js:549-550 reads local files with fs.createReadStream(content.path).
• shared.resolveContent() does not check disableFileAccess or disableUrlAccess and does not receive those flags.

Control path showing intended enforcement:

• lib/mail-composer/index.js:358-359, lib/mail-composer/index.js:367-368, and sibling child-node creation paths pass disableUrlAccess and disableFileAccess into MimeNode.
• lib/mime-node/index.js:51-52 stores those flags.
• lib/mime-node/index.js:984-995 rejects file paths with EFILEACCESS when disableFileAccess is set.
• lib/mime-node/index.js:998-1009 rejects URLs with EURLACCESS when disableUrlAccess is set.
• test/mail-composer/mail-composer-test.js:1028-1044 includes a normal MIME-streaming test that expects file access to be blocked when disableFileAccess: true.

Additional same-root-cause variant:

• lib/mailer/index.js:406-434 implements _convertDataImages() for attachDataUrls.
• lib/mailer/index.js:407-410 calls mail.resolveContent(mail.data, 'html', ...) when attachDataUrls is enabled and mail.data.html is present.
• Because mail.resolveContent() delegates to shared.resolveContent() at lib/mailer/mail-message.js:42-44, an object-form html: { path: ... } or html: { href: ... } can be resolved before the later MIME streaming enforcement sees the content.
• This variant requires attachDataUrls to be enabled, so the main reportable default/common path is jsonTransport; both should be fixed by enforcing access flags inside the pre-resolution helper or passing policy into it.

Default/common exposure evidence:

• jsonTransport is a shipped runtime transport selected by public createTransport options.
• test/json-transport/json-transport-test.js:9-83 demonstrates that jsonTransport intentionally resolves file-backed html and attachments into JSON output.
• disableFileAccess and disableUrlAccess are documented by code and tests as security controls and are copied from transport…

Nodemailer before 8.0.9 fails to enforce disableFileAccess and disableUrlAccess options during message normalization in jsonTransport. Attackers can read local files or fetch URLs by supplying path or href values in message content fields, bypassing intended access controls.

Nodemailer before 8.0.9 fails to enforce disableFileAccess and disableUrlAccess options during message normalization in jsonTransport. Attackers can read local files or fetch URLs by supplying path or href values in message content fields, bypassing intended access controls.