Race condition in multer - CVE-2026-77063

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Main Vulnerability Database Vulnerabilities #VU146780

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
Automation Assets in IBM Cloud Pak for Integration (CP4I)

How to mitigate CVE-2026-77063

Install security update from vendor's website.

multer - update to 2.3.0
Automation Assets in IBM Cloud Pak for Integration (CP4I) - addressed in versions 4.0.26-sc2, 4.4.3

External References

Related Security Bulletins