{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-5079: multer vulnerable to Denial of Service via deeply nested field names","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-5079","status":"final","version":"1","initial_release_date":"2026-06-15T13:56:45.520Z","current_release_date":"2026-06-15T16:00:43.955Z","revision_history":[{"date":"2026-06-15T13:56:45.520Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"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.","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-5079 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-5079"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-5079"},{"category":"external","summary":"github.com","url":"https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24j"},{"category":"external","summary":"cna.openjsf.org","url":"https://cna.openjsf.org/security-advisories.html"}]},"product_tree":{"branches":[{"category":"vendor","name":"multer","branches":[{"category":"product_name","name":"multer","branches":[{"category":"product_version_range","name":">=1.0.0 <2.2.0","product":{"name":"multer multer >=1.0.0 <2.2.0","product_id":"CSAFPID-1","product_identification_helper":{"cpe":"cpe:2.3:a:multer:multer:*:*:*:*:*:*:*:*"}}},{"category":"product_version_range","name":">=3.0.0-alpha.1 <3.0.0-alpha.2","product":{"name":"multer multer >=3.0.0-alpha.1 <3.0.0-alpha.2","product_id":"CSAFPID-2","product_identification_helper":{"cpe":"cpe:2.3:a:multer:multer:*:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"2.2.0","product":{"name":"multer multer 2.2.0","product_id":"CSAFPID-3","product_identification_helper":{"cpe":"cpe:2.3:a:multer:multer:*:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"3.0.0-alpha.2","product":{"name":"multer multer 3.0.0-alpha.2","product_id":"CSAFPID-4","product_identification_helper":{"cpe":"cpe:2.3:a:multer:multer:*:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-5079","title":"multer vulnerable to Denial of Service via deeply nested field names","notes":[{"category":"description","text":"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.","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1","CSAFPID-2"],"fixed":["CSAFPID-3","CSAFPID-4"]},"scores":[{"cvss_v3":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"products":["CSAFPID-1","CSAFPID-2"]}],"remediations":[{"category":"vendor_fix","details":"Update to a fixed version: 2.2.0, 3.0.0-alpha.2.","product_ids":["CSAFPID-1","CSAFPID-2"]}]}]}