CVE-2026-77063

Summary

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.

Affected Software

Weaknesses

• CWE-362: CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

References

• https://github.com/expressjs/multer/security/advisories/GHSA-qvfw-j98x-7q72
• https://cna.openjsf.org/security-advisories.html

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