# CVE-2025-47944: Multer denial of service from malformed multipart requests

Source: https://junglewise.ai/threats/cve-2025-47944-multer-denial-of-service-from-malformed-multipart-requests  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-05-19. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2025-47944 · Severity: low · CVSS 3.1 · Published 2025-05-19

Multer is a widely-used Node.js middleware for handling file uploads in web applications. A vulnerability in versions 1.4.4-lts.1 through 1.x allows attackers to crash the application by sending malformed file upload requests, causing service downtime and potential denial of service attacks against any web application using affected versions.

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

## Quick answers

**Is CVE-2025-47944 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-47944 being exploited in the wild.

**How severe is CVE-2025-47944?** Low severity, with a CVSS score of 3.1, published 19 May 2025.

**Which products and versions are affected?** multer (npm) SEMVER:introduced=1.4.4-lts.1,fixed=2.0.0.

**Is there a fix for CVE-2025-47944?** Yes. multer (npm): upgrade to 2.0.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2025-47944 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2025-47944?** Check whether you run multer (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

- multer (npm): upgrade to 2.0.0 or later

  ```sh
  npm install multer@2.0.0
  ```


## Technical details

The vulnerability is an uncaught exception (CWE-248) in Multer's handling of malformed multipart/form-data upload requests. Specifically, an error event from the underlying busboy stream parser is not properly caught and handled, causing an unhandled exception that crashes the Node.js process. The attack requires only network access and no authentication or special privileges; an attacker can trigger the crash by sending a crafted multipart request with malformed structure. This affects all versions from 1.4.4-lts.1 to <2.0.0. The fix involves explicitly handling busboy error events and properly draining the request stream, which was addressed in version 2.0.0.

## Affected products

- expressjs multer >=1.4.4-lts.1, <2.0.0

## Identifiers

- CVE-2025-47944
- GHSA-4pg4-qvpc-4q3h

## Timeline

- 2025-05-19: disclosed: GHSA-4pg4-qvpc-4q3h published
- 2025-05-19: patched: Version 2.0.0 released with fix

## References

- [https://github.com/expressjs/multer/security/advisories/GHSA-4pg4-qvpc-4q3h](https://github.com/expressjs/multer/security/advisories/GHSA-4pg4-qvpc-4q3h)
- [https://github.com/expressjs/multer/issues/1176](https://github.com/expressjs/multer/issues/1176)
- [https://github.com/expressjs/multer/commit/2c8505f207d923dd8de13a9f93a4563e59933665](https://github.com/expressjs/multer/commit/2c8505f207d923dd8de13a9f93a4563e59933665)
- [https://github.com/expressjs/multer](https://github.com/expressjs/multer)

## Related threats

- [multer denial of service in asynchronous fileFilter after request teardown](https://junglewise.ai/threats/cve-2026-113872-multer-is-a-middleware-for-node-js-that-handles-multipart-form)
- [Express multer Denial of Service via orphaned disk writes](https://junglewise.ai/threats/cve-2026-88932-express-multer-denial-of-service-via-orphaned-disk-writes)
- [multer denial of service via oversized array index](https://junglewise.ai/threats/cve-2026-82333-multer-denial-of-service-via-oversized-array-index-in-field-names)
- [multer Denial of Service via crafted multipart field names](https://junglewise.ai/threats/cve-2026-77078-multer-denial-of-service-via-crafted-multipart-field-names)
- [multer file size limit bypass via async fileFilter race condition](https://junglewise.ai/threats/cve-2026-77063-multer-file-size-limit-bypass-via-async-filefilter-race-condition)