CVE-2026-77063
multer vulnerable to file size limit bypass via async fileFilter race condition
CVSS Score
3.7
EPSS Score
0.0%
EPSS Percentile
0th
multer is a middleware for handling multipart/form-data in Node.js. When an application uses an asynchronous fileFilter together with the fileSize limit, a race condition in multer's file stream handling can allow a file that exceeds the configured size limit to bypass the size-limit rejection. All versions before 2.3.0 are affected. The impact is limited because the underlying multipart parser still truncates the stream at the size limit, so this is a bypass of the limit rejection rather than uncontrolled resource consumption. The issue is fixed in multer 2.3.0. Upgrade to multer 2.3.0 to remediate.
| CWE | CWE-362 |
| Vendor | multer |
| Product | multer |
| Published | Aug 28, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability
Affected Versions
multer / multer
0 < 2.3.0
References
Credits
🔍 ThinkerHao bjohansebas UlisesGascon