What’s Vulnerable › Vulnerabilities

CVE-2026-27492: Lettermint Node.js SDK leaks email properties to unintended recipients when client instance is reused

• Severity: medium (CVSS 4.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-21 · updated 2026-06-17
• Weakness: CWE-488

Description

Lettermint Node.js SDK is the official Node.js SDK for Lettermint. In versions 1.5.0 and below, email properties (such as to, subject, html, text, and attachments) are not reset between sends when a single client instance is reused across multiple .send() calls. This can cause properties from a previous send to leak into a subsequent one, potentially delivering content or recipient addresses to unintended parties. Applications sending emails to different recipients in sequence — such as transactional flows like password resets or notifications — are affected. This issue has been fixed in version 1.5.1.

Affected products

• lettermint-node: before 1.5.1 — fixed in 1.5.1

How to fix

Upgrade to a fixed version: lettermint-node 1.5.1. Check the vendor advisory for mitigations.

References

• https://github.com/lettermint/lettermint-node/blob/main/CHANGELOG.md#151-2026-02-20
• https://github.com/lettermint/lettermint-node/commit/24a17acbc2429c5eb30391f9df3dc0ea7aaf4de1
• https://github.com/lettermint/lettermint-node/security/advisories/GHSA-49pc-8936-wvfp

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