Race condition in multer - CVE-2026-77063
Published: September 2, 2026
Vulnerability identifier: #VU146780
CSH Severity: Low
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-77063
CWE-ID: CWE-362
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass file size restrictions on uploaded files.
The vulnerability exists due to a race condition in the asynchronous fileFilter handling in multer when processing file uploads with an asynchronous fileFilter. A remote attacker can upload an oversized file to bypass file size restrictions on uploaded files.
Only uploads using an asynchronous fileFilter are affected; uploads using a synchronous fileFilter are not affected.
Affected software
multer
How to mitigate CVE-2026-77063
Install security update from vendor's website.
multer - update to 2.3.0