GHSA-qvfw-j98x-7q72

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    GHSA-qvfw-j98x-7q72

    Published: 8 Sept 2026Last Modified: 8 Sept 2026

    Summary: multer vulnerable to file size limit bypass via async fileFilter race condition

    Details: ### Impact When `multer` is configured with an asynchronous `fileFilter`, the `limits.fileSize` limit can be bypassed. The `'limit'` event is registered inside the async `fileFilter` callback, so if a file exceeds `limits.fileSize` before that callback runs, the event is missed and the oversized upload is accepted instead of being rejected with a `LIMIT_FILE_SIZE` error. Applications that rely on `limits.fileSize` to reject oversized uploads are affected on all upload methods (`.single()`, `.array()`, `.fields()`, `.any()`). Uploads using a synchronous `fileFilter` are not affected. ### Patches Users should upgrade to `2.3.0`. ### Workarounds Use a synchronous `fileFilter`, or validate the uploaded file size after the upload completes.

    References: https://github.com/expressjs/multer/security/advisories/GHSA-qvfw-j98x-7q72, https://nvd.nist.gov/vuln/detail/CVE-2026-77063, https://github.com/expressjs/multer/commit/ab6aeae650328cf31799dcfa4c3e116ba8faaacc, https://cna.openjsf.org/security-advisories.html, https://github.com/expressjs/multer, https://github.com/expressjs/multer/releases/tag/v2.3.0

    Affected packages

    Package

    Name: multer

    Purl: pkg:npm/multer

    Affected ranges

    Type: SEMVER

    Events:

    Introduced- 0
    Fixed -2.3.0

    Affected versions

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High