Critical Malicious Code Vulnerability in js-multer Package
Summary
MAL-2026-1016: Malicious code in js-multer (npm). Affected versions are not published. No fix is published. 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 js-multer package is a middleware for handling multipart/form-data, primarily used for uploading files in Node.js applications. It simplifies the process of handling file uploads, making it a popular choice among developers. However, the package has been compromised, leading to severe security risks for any application utilizing it.
Vulnerability Detail
The vulnerability originates from malicious code embedded within the js-multer package. This code can fully compromise any computer that has the package installed or running, potentially allowing unauthorized access to sensitive information such as secrets and keys. The malicious nature of the code is classified under CWE-506, indicating that it contains embedded malicious code that poses significant risks to the integrity and security of affected systems.
How To Fix
This package is malicious. Remove it and rotate any credentials it could have accessed.
npm uninstall js-multerIf it arrived as a transitive dependency, remove the package that pulled it in, then reinstall.
Tip — Not sure whether your app is affected? Vulert can check the versions your app actually runs. Scan free →
Workaround
As a workaround, you can temporarily halt the use of the js-multer package and switch to alternative middleware for handling file uploads, such as multer or busboy, until the issue is resolved.
Conclusion
The js-multer package has been identified as containing malicious code that poses significant security risks. Immediate action is required to remove the package and secure any sensitive information. Users are encouraged to monitor for updates and consider alternative solutions for file uploads.
See every vulnerability recorded for js-multer →
FAQ
js-multer is a middleware for Node.js that simplifies the handling of multipart/form-data, primarily used for file uploads.
You can check if your application is affected by using Vulert, which monitors open-source vulnerabilities in real-time. Visit Vulert Scanner to analyze your package-lock.json without any signup.
Immediately remove the js-multer package from your application and rotate any sensitive information stored on the affected system.
Currently, there is no patched version available. It is crucial to remove the package and monitor for updates.
Failing to address this vulnerability can lead to unauthorized access to sensitive data, complete system compromise, and potential data breaches.
