CodeQL documentation

Exposure of private files

ID: js/exposure-of-private-files
Kind: problem
Severity: warning
Precision: high
   - security
   - external/cwe/cwe-200
Query suites:
   - javascript-code-scanning.qls
   - javascript-security-extended.qls
   - javascript-security-and-quality.qls

Click to see the query in the CodeQL repository

Libraries like express provide easy methods for serving entire directories of static files from a web server. However, using these can sometimes lead to accidental information exposure. If for example the node_modules folder is served, then an attacker can access the _where field from a package.json file, which gives access to the absolute path of the file.


Limit which folders of static files are served from a web server.


In the example below, all the files from the node_modules are served. This allows clients to easily access all the files inside that folder, which includes potentially private information inside package.json files.

var express = require('express');

var app = express();

app.use('/node_modules', express.static(path.resolve(__dirname, '../node_modules')));

The issue has been fixed below by only serving specific folders within the node_modules folder.

var express = require('express');

var app = express();

app.use("jquery", express.static('./node_modules/jquery/dist'));
app.use("bootstrap", express.static('./node_modules/bootstrap/dist'));