Executive brief
Multer is a popular software component used by web applications to handle file uploads. A security flaw in this component allows an attacker to crash the service or make it unresponsive by repeatedly starting and then abruptly dropping file upload connections. This can lead to a total service outage, preventing legitimate users from accessing the application.
Technical details
A Denial of Service (DoS) vulnerability exists in Multer due to improper handling of aborted connections during multipart/form-data uploads. The root cause is a failure to release system resources (CWE-772) when a client abruptly terminates a connection while a file is being uploaded. An unauthenticated remote attacker can exploit this by initiating multiple concurrent uploads and dropping the connections, leading to resource exhaustion and service unavailability. The issue is addressed in version 2.1.0 by improving disconnect handling and ensuring cleanup of aborted uploads.
Affected products
- expressjs multer < 2.1.0
Timeline
- 2026-02-27: advisory: Initial advisory published by OpenJS Foundation
- 2026-02-27: patched: Version 2.1.0 released with fix
References
- https://cna.openjsf.org/security-advisories.html
- https://github.com/expressjs/multer/commit/cccf0fe0e64150c4f42ccf6654165c0d66b9adab
- https://github.com/expressjs/multer/security/advisories/GHSA-v52c-386h-88mc
- https://www.cve.org/CVERecord?id=CVE-2026-2359
- https://access.redhat.com/errata/RHSA-2026:6174
- https://access.redhat.com/errata/RHSA-2026:6802
- https://access.redhat.com/security/cve/CVE-2026-2359