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The CVE-2025-XXXXX vulnerability in Mailgen stems from improper neutralization of user-supplied input during the generation of plaintext emails. The `Mailgen.generatePlaintext(email)` method fails to adequately sanitize content that contains HTML tags. When user-controlled data containing HTML elements is passed to this method, the library’s internal conversion process does not escape these tags. Consequently, the HTML tags are rendered verbatim in the plaintext output. This occurs because the method attempts to create a text-based version by stripping HTML, but the logic is incomplete. A malicious actor can exploit this by crafting input with HTML tags, which, while intended for plaintext, are not properly handled and can lead to misinterpretation of the email content by downstream systems or parsers that might process the plaintext in an unsafe context, leading to a limited HTML injection.
Platform: Node.js/npm
Version: <2.0.30
Vulnerability : HTML Injection
Severity: Low
date: 2024-09-22
Prediction: Patch available
What Undercode Say:
Simulating the vulnerable method input
echo "<script>alert('XSS')</script>User content" > user_input.txt
cat user_input.txt | node -e "
const mailgen = require('mailgen');
let mg = new mailgen({theme: 'default', product: {name: 'Test', link: 'http://test.com'}});
let email = { body: { intro: require('fs').readFileSync(0, 'utf8') } };
console.log(mg.generatePlaintext(email));
"
// Example of vulnerable code path before patch
function generatePlaintext(email) {
let html = generateHTML(email); // Generates HTML first
// Flawed conversion: simple regex replacement misses edge cases
let plaintext = html.replace(/<[^>]>/g, ''); // Incomplete sanitization
return plaintext;
}
How Exploit:
An attacker supplies crafted input with HTML tags into data fields processed by generatePlaintext. The tags are not escaped and appear raw in the output.
Protection from this CVE
Upgrade Mailgen to version 2.0.30 or later. Apply input sanitization to user-generated content before passing it to the library.
Impact:
Limited HTML injection in plaintext email output, potentially affecting downstream processing systems.
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Sources:
Reported By: github.com
Extra Source Hub:
Undercode
