GHSA-535w-7cp7-47q4

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    GHSA-535w-7cp7-47q4

    Published: 8 Sept 2026Last Modified: 8 Sept 2026

    Summary: multer vulnerable to Denial of Service via oversized array index in field names

    Details: ### Impact multer is vulnerable to a Denial of Service (DoS) via a crafted array index in multipart field names. The `append-field` dependency parses bracket notation in field names, and a large numeric index such as `items[4294967294]` forces allocation of a maximum-length sparse array. A following field with a non-numeric key on the same base then converts that array to an object by iterating its full length, which consumes CPU synchronously and leaves the process unable to handle other requests. A single HTTP request with a crafted multipart body is sufficient to exploit this, and it affects multer 1.x and 2.x. ### Patches Users should upgrade to `2.3.0` and configure `limits.fieldArrayIndexLimit` to the minimum array index their application requires. ### Workarounds None.

    References: https://github.com/expressjs/multer/security/advisories/GHSA-535w-7cp7-47q4, https://nvd.nist.gov/vuln/detail/CVE-2026-82333, https://github.com/expressjs/multer/pull/1438, https://github.com/expressjs/multer/commit/73c1759fa93b87366bc6dbd7abe1b80ddff7d27c, 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