CVE-2020-7699: Prototype Pollution in express-fileupload
Summary
CVE-2020-7699: Prototype Pollution in express-fileupload. Affects express-fileupload versions < 1.1.9. Fixed in 1.1.9. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
The package under scrutiny is express-fileupload, an npm package used for handling file uploads in Express.js applications. It provides middleware that allows users to easily handle file uploads and integrates with the Express.js framework. The package is vulnerable to a prototype pollution vulnerability when the parseNested option is enabled. This vulnerability can lead to denial of service or arbitrary code execution if a corrupt HTTP request is sent.
Vulnerability Detail
The vulnerability, identified as CVE-2020-7699, is a prototype pollution issue in express-fileupload before version 1.1.8. When the parseNested option is enabled, an attacker can exploit this vulnerability by sending a corrupt HTTP request. This can result in denial of service or arbitrary code execution. Prototype pollution is a vulnerability that occurs when an attacker can inject properties into existing objects, potentially leading to the modification of behavior or the execution of arbitrary code.
How To Fix
Latest published version: 1.5.2 as of 23 Oct 2026
npm install express-fileupload@1.5.2Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
1.1.9
This is the first release that contains the fix.
npm install express-fileupload@1.1.9Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If updating the package is not immediately feasible, a possible workaround is to disable the parseNested option in the express-fileupload configuration. This can be done by setting the parseNested option to false when initializing the express-fileupload middleware. Here's an example:
const express = require('express');
const fileUpload = require('express-fileupload');
const app = express();
app.use(fileUpload({
parseNested: false
}));
Conclusion
In conclusion, the express-fileupload package before version 1.1.8 is vulnerable to prototype pollution when the parseNested option is enabled. This can result in denial of service or arbitrary code execution. It is recommended to update the package to version 1.1.9 or later to fix the vulnerability. If updating is not possible immediately, a workaround is available by disabling the parseNested option. For further support on vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for express-fileupload →
FAQ
express-fileupload is an npm package used for handling file uploads in Express.js applications. It provides middleware that simplifies the process of handling file uploads and integrates with the Express.js framework.
Prototype pollution is a vulnerability that occurs when an attacker can inject properties into existing objects, potentially leading to the modification of behavior or the execution of arbitrary code.
The impact of this vulnerability can range from denial of service to arbitrary code execution. An attacker can exploit the vulnerability by sending a corrupt HTTP request when the parseNested option is enabled in express-fileupload.
To fix this vulnerability, it is recommended to update the express-fileupload package to version 1.1.9 or later. This version includes a fix for the prototype pollution issue. Updating the package can be done by running the command 'npm update express-fileupload'.
Yes, if updating the package is not immediately feasible, a possible workaround is to disable the parseNested option in the express-fileupload configuration. This can be done by setting the parseNested option to false when initializing the express-fileupload middleware.
References
Related vulnerabilities
Recent vulnerabilities recorded for express-fileupload.
