CVE-2025-62366: mailgen is a Node.js package that generates responsive HTML e-mails for sending transactional mail.

mailgen is a Node.js package that generates responsive HTML e-mails for sending transactional mail.

mailgen is a Node.js package that generates responsive HTML e-mails for sending transactional mail. Mailgen versions through 2.0.30 contain an HTML injection vulnerability in plaintext emails produced by the generatePlaintext method when user‑generated content is supplied. The function attempts to remove HTML tags, but if tags are provided as encoded HTML entities they are not removed and are later decoded, resulting in active HTML (for example an img tag with an event handler) in the supposed plaintext output. In contexts where the generated plaintext string is subsequently rendered as HTML, this can allow execution of attacker‑controlled JavaScript. Versions 2.0.31 and later contain a fix. No known workarounds exist.

Description from the National Vulnerability Database, published by GitHub

What it means for a small business

If your business uses mailgen, install the vendor's update. If you're not sure whether you use it, ask whoever manages your computers.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.43%, higher than 37% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

Check your own setup

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Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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