# express-fileupload denial of service in filename processing

Source: https://junglewise.ai/threats/express-fileupload-denial-of-service-in-filename-processing-efdc3134  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2020-09-03. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

Severity: info · Published 2020-09-03

express-fileupload is a Node.js library that handles file uploads in web applications. Versions prior to 1.1.6-alpha.6 contain a flaw that causes the server to delay responses for up to 30 seconds when processing requests with large filenames containing many dot characters. An attacker can exploit this by sending specially crafted upload requests to temporarily exhaust server responsiveness and degrade service for legitimate users.

Technologies: [express-fileupload (npm)](https://junglewise.ai/threats/technologies/express-fileupload). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Informational severity, published 3 September 2020.

**Which products and versions are affected?** express-fileupload (npm) SEMVER:introduced=0,fixed=1.1.6-alpha.6.

**Is there a fix for This vulnerability?** Yes. express-fileupload (npm): upgrade to 1.1.6-alpha.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run express-fileupload (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- express-fileupload (npm): upgrade to 1.1.6-alpha.6 or later

  ```sh
  npm install express-fileupload@1.1.6-alpha.6
  ```


## Technical details

The vulnerability is a denial-of-service condition caused by inefficient processing of filenames containing a large number of dot (.) characters. When express-fileupload processes such filenames, it exhibits significant performance degradation, causing server response delays of up to 30 seconds in testing. The flaw is triggered during the normal request handling path with no authentication or special preconditions required; any network-reachable endpoint using vulnerable versions is susceptible. An attacker can craft HTTP requests with large dot-filled filenames to repeatedly trigger delays and degrade service availability. The vulnerability was fixed in version 1.1.6-alpha.6 and later; upgrading resolves the issue.

## Affected products

- express-fileupload prior to 1.1.6-alpha.6

## Timeline

- 2020-09-03: disclosed

## References

- [https://www.npmjs.com/advisories/1216](https://www.npmjs.com/advisories/1216)

## Related threats

- [Express-FileUpload arbitrary file overwrite](https://junglewise.ai/threats/cve-2022-27261-express-fileupload-arbitrary-file-overwrite)
- [express-fileupload prototype pollution in nested parsing](https://junglewise.ai/threats/cve-2020-7699-express-fileupload-prototype-pollution-in-nested-parsing)