CVE-2026-88932: multer vulnerable to Denial of Service via orphaned disk writes on aborted uploads
Impact
Multer's diskStorage can leave complete, orphaned files on disk when a multipart upload is aborted in the brief window before the storage engine assigns the file path. This is an incomplete fix of CVE-2026-5038: the earlier cleanup removes only in-flight uploads that already have a path, so an upload aborted inside that window is written to disk with nothing left to remove it, and the application is not given a handle to clean it up. An unauthenticated attacker sending aborted requests to any route backed by disk storage can accumulate orphaned files until the upload directory or the shared system temporary directory is exhausted. An asynchronous destination or filename widens the window.
Patches
Users should upgrade to 2.4.0 or higher.
Workarounds
None.
Other sources
multer is a Node.js middleware for handling multipart/form-data uploads. In versions 2.2.0 through 2.3.0, when a request using disk storage is aborted mid-upload, file writes that complete after multer has already run its abort cleanup are not removed, so each aborted upload can leave an orphaned file on disk. A remote unauthenticated attacker can repeatedly start and abort uploads to accumulate orphaned files and exhaust disk space, causing a denial of service. The issue is fixed in multer 2.4.0, and users should upgrade to 2.4.0 or later.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/multerto a version that resolves this vulnerability.Fixed in 2.4.0 - Upgrade
Upgrade
multerto a version that resolves this vulnerability.Fixed in 2.4.0
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using multer versions 2.2.0 through 2.3.0 with disk storage are affected. The problem occurs when multipart/form-data uploads are aborted while file writes are still completing.
What does an attacker need to do to exploit it?
An attacker needs only network access to an upload endpoint that uses the affected disk-storage configuration. They can repeatedly begin and abort uploads, without authentication or user interaction, to leave files behind and consume disk space.
Does upgrading resolve existing disk consumption?
Upgrading to multer 2.4.0 or later fixes the orphaned-write behavior for future aborted uploads. The provided information does not state that an upgrade removes files already orphaned on disk.
How can I determine whether I may be affected?
Check whether your application uses multer 2.2.0 through 2.3.0 and is configured for disk storage. Systems with upload endpoints may also need to inspect their upload storage locations for files left by aborted uploads.