CVE-2026-77063

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-28 22:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-02 14:46 UTC Last updatedMost recent change to the record

Details

Published

2026-08-28 22:16 UTC

Last modified

2026-09-02 14:46 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-362 · Race condition

Record status

Analyzed

Affected

• Expressjs Multer < 2.3.0

Attack profile CVSS 3.1 · 3.7

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None