{"id":"CVE-2026-5079","aliases":["GHSA-72gw-mp4g-v24j"],"url":"https://o3.security/vulnerability/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.","published":"2026-06-15T13:56:45.520Z","modified":"2026-08-12T03:51:35.927456203Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.00278,"percentile":0.20152,"asOf":"2026-08-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"multer","fixedVersion":"2.2.0"},{"ecosystem":"npm","name":"multer","fixedVersion":"3.0.0-alpha.2"}],"fix":null,"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:35.927456203Z"}}