CVE-2025-62366
CVE-2025-62366 is a Cross-site Scripting (XSS) vulnerability in mailgen. O3 Security confirms whether CVE-2025-62366 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Mailgen vulnerable to HTML injection and cross-site scripting via plaintext email generation
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
mailgennpmDescription
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | mailgen | all versions | 2.0.31 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mailgen. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update mailgen to 2.0.31 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-62366 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-62366 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-62366. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-62366 in your dependencies?
O3 detects CVE-2025-62366 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.