{"id":"CVE-2026-5079","summary":"multer vulnerable to Denial of Service via deeply nested field names","details":"Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this.\n\nPatches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires.\n\nWorkarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.","aliases":["GHSA-72gw-mp4g-v24j"],"modified":"2026-07-16T03:46:07.619177884Z","published":"2026-06-15T13:56:45.520Z","database_specific":{"cna_assigner":"openjs","cwe_ids":["CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5079.json"},"references":[{"type":"ADVISORY","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5079.json"},{"type":"ADVISORY","url":"https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24j"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5079"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/expressjs/multer","events":[{"introduced":"869e2138af1d2b9cf62b8abb95e5785aef007b4b"},{"fixed":"2e2af08157c66cbbc76539ccbd8869097a0c8feb"}],"database_specific":{"cpe":"cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:*","extracted_events":[{"introduced":"1.0.0"},{"fixed":"2.2.0"}],"source":"CPE_RANGE"}}],"versions":["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-2026-5079.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}