{"id":"GHSA-qvfw-j98x-7q72","summary":"multer vulnerable to file size limit bypass via async fileFilter race condition","details":"### Impact\n\nWhen `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.\n\n### Patches\n\nUsers should upgrade to `2.3.0`.\n\n### Workarounds\n\nUse a synchronous `fileFilter`, or validate the uploaded file size after the upload completes.","aliases":["CVE-2026-77063"],"modified":"2026-09-08T21:45:04.622654725Z","published":"2026-09-08T21:29:42Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-09-08T21:29:42Z","nvd_published_at":"2026-08-28T22:16:53Z","cwe_ids":["CWE-362"],"severity":"LOW"},"references":[{"type":"WEB","url":"https://github.com/expressjs/multer/security/advisories/GHSA-qvfw-j98x-7q72"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-77063"},{"type":"WEB","url":"https://github.com/expressjs/multer/commit/ab6aeae650328cf31799dcfa4c3e116ba8faaacc"},{"type":"WEB","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"PACKAGE","url":"https://github.com/expressjs/multer"},{"type":"WEB","url":"https://github.com/expressjs/multer/releases/tag/v2.3.0"}],"affected":[{"package":{"name":"multer","ecosystem":"npm","purl":"pkg:npm/multer"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-qvfw-j98x-7q72/GHSA-qvfw-j98x-7q72.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}