GHSA-qvfw-j98x-7q72
multer vulnerable to file size limit bypass via async fileFilter race condition
At a glance
- Published
- Updated
- CVE
- CVE-2026-77063
- CVSS_V3
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Description
### 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 `LIMIT_FILE_SIZE` 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.
Affected packages
| Package | Versions |
|---|---|
| npm · multer | introduced 0, fixed 2.3.0 |
References
- https://github.com/expressjs/multer/security/advisories/GHSA-qvfw-j98x-7q72 WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-77063 ADVISORY
- https://github.com/expressjs/multer/commit/ab6aeae650328cf31799dcfa4c3e116ba8faaacc WEB
- https://cna.openjsf.org/security-advisories.html WEB
- https://github.com/expressjs/multer PACKAGE
- https://github.com/expressjs/multer/releases/tag/v2.3.0 WEB
Sources
| Source | Licence |
|---|---|
| OSV.dev | CC-BY 4.0 — GitHub Advisory Database |