How severe is CVE-2025-62366?

No CVSS score has been assigned to CVE-2025-62366 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-62366?

CVE-2025-62366 affects the following packages: mailgen (npm). Ecosystems affected: npm.

How do I fix CVE-2025-62366?

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.

How do I detect CVE-2025-62366 in my npm dependencies?

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.

How do I mitigate CVE-2025-62366 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2025-62366?

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.

Is CVE-2025-62366 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-62366 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-62366?

CVE-2025-62366 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 30th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-62366?

CVE-2025-62366 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2025-62366 published, and has it been updated?

CVE-2025-62366 was published on October 14, 2025 and was last updated on April 2, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2025-62366: mailgen

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk30th percentile+0.26%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.

mailgennpm

13Kdownloads / week

Description

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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`mailgen`	all versions	2.0.31

Detection & mitigation playbook

Open-source dependency

Detect
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

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,

O3 Security · Impact-Aware SCA

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.

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CVE-2025-62366