Impact
A vulnerability in Multer versions < 2.1.0 allows an attacker to trigger a Denial of Service (DoS) by dropping connection during file upload, potentially causing resource exhaustion.
Patches
Users should upgrade to 2.1.0
Workarounds
None
Impact
A vulnerability in Multer versions < 2.1.0 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing resource exhaustion.
Patches
Users should upgrade to 2.1.0
Workarounds
None
Impact
A vulnerability in Multer versions < 2.1.1 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing stack overflow.
Patches
Users should upgrade to 2.1.1
Workarounds
None
Resources
- https://github.com/expressjs/multer/security/advisories/GHSA-5528-5vmv-3xc2 - https://www.cve.org/CVERecord?id=CVE-2026-3520 - https://github.com/expressjs/multer/commit/7e66481f8b2e6c54b982b34c152479e096ce2752 - https://cna.openjsf.org/security-advisories.html
Impact
Multer is vulnerable to a Denial of Service (DoS) via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names (e.g., a[b][c]) with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this.
Patches
Users should upgrade to 2.2.0 and configure limits.fieldNestingDepth to the minimum depth their application requires.
Workarounds
Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.
Impact
A vulnerability in Multer allows an attacker to trigger a Denial of Service (DoS) by aborting or sending malformed multipart uploads, causing orphaned partial files to accumulate on disk when using diskStorage.
Patches
Users should upgrade to 2.2.0, 3.0.0-alpha.2 or higher
Workarounds
None
Impact
multer is vulnerable to a Denial of Service (DoS) via a crafted array index in multipart field names. The append-field dependency parses bracket notation in field names, and a large numeric index such as items[4294967294] forces allocation of a maximum-length sparse array. A following field with a non-numeric key on the same base then converts that array to an object by iterating its full length, which consumes CPU synchronously and leaves the process unable to handle other requests. A single HTTP request with a crafted multipart body is sufficient to exploit this, and it affects multer 1.x and 2.x.
Patches
Users should upgrade to 2.3.0 and configure limits.fieldArrayIndexLimit to the minimum array index their application requires.
Workarounds
None.
Impact
A vulnerability in multer 2.2.0 allows an attacker to trigger a Denial of Service (DoS) by aborting or truncating multipart uploads. When using diskStorage, the destination write stream is not closed if the upload is aborted before it finishes, so each failed request leaks an open file descriptor and retains its disk blocks until the process exits. Repeated failed uploads can exhaust the available file descriptors. All applications using multer's disk storage are affected.
Patches
Users should upgrade to 2.3.0.
Workarounds
None.
Impact
A vulnerability in multer allows a remote, unauthenticated attacker to crash the Node.js process with a single multipart/form-data request. Two specially crafted text field names cause an uncaught RangeError: Invalid array length inside multer's field parsing, which is not routed to the application error handler and terminates the process. All applications using multer to parse multipart requests are affected.
Patches
Users should upgrade to 2.3.0.
Workarounds
None.
Multer is a node.js middleware for handling multipart/form-data. A vulnerability in Multer prior to version 2.1.0 allows an attacker to trigger a Denial of Service (DoS) by dropping connection during file upload, potentially causing resource exhaustion. Users should upgrade to version 2.1.0 to receive a patch. No known workarounds are available.
Multer is a node.js middleware for handling multipart/form-data. A vulnerability in Multer prior to version 2.1.0 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing resource exhaustion. Users should upgrade to version 2.1.0 to receive a patch. No known workarounds are available.
Multer is a node.js middleware for handling multipart/form-data. A vulnerability in Multer prior to version 2.1.1 allows an attacker to trigger a Denial of Service (DoS) by sending malformed requests, potentially causing stack overflow. Users should upgrade to version 2.1.1 to receive a patch. No known workarounds are available.
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.
Impact
When multer is configured with an asynchronous fileFilter, the limits.fileSize limit can be bypassed. The 'limit' event is registered inside the async fileFilter callback, so if a file exceeds limits.fileSize before that callback runs, the event is missed and the oversized upload is accepted instead of being rejected with a LIMITFILESIZE error. Applications that rely on limits.fileSize to reject oversized uploads are affected on all upload methods (.single(), .array(), .fields(), .any()). Uploads using a synchronous fileFilter are not affected.
Patches
Users should upgrade to 2.3.0.
Workarounds
Use a synchronous fileFilter, or validate the uploaded file size after the upload completes.