{"id":"CVE-2026-77063","summary":"multer vulnerable to file size limit bypass via async fileFilter race condition","details":"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.","aliases":["GHSA-qvfw-j98x-7q72"],"modified":"2026-09-05T03:48:00.658542071Z","published":"2026-08-28T19:54:58.473Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77063.json","cna_assigner":"openjs","cwe_ids":["CWE-362"]},"references":[{"type":"ADVISORY","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77063.json"},{"type":"ADVISORY","url":"https://github.com/expressjs/multer/security/advisories/GHSA-qvfw-j98x-7q72"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-77063"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/expressjs/multer","events":[{"introduced":"0"},{"fixed":"4e8edf50dbb5ddec213b6253642cbc08ce0225a7"}],"database_specific":{"cpe":"cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:*","extracted_events":[{"introduced":"0"},{"fixed":"2.3.0"}],"source":["AFFECTED_FIELD","CPE_RANGE"]}}],"versions":["v2.2.0","v2.1.1","v2.1.0","v2.0.2","v2.0.1","v2.0.0","v1.4.5-lts.2","v1.4.5-lts.1","v1.4.4","v1.4.4-lts.1","v1.4.3","v1.4.2","v1.4.1","v1.4.0","v1.3.1","v1.3.0","v1.2.1","v1.2.0","v1.1.0","v1.0.6","v1.0.5","v1.0.4","v1.0.3","v1.0.2","v1.0.1","v1.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-77063.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"}]}