{"id":"CVE-2026-128336","aliases":[],"cve":{"records":[{"id":"CVE-2026-128336","source":"VulnCheck","state":"PUBLISHED","reasons":[],"replacements":[],"disputed":false,"unsupportedWhenAssigned":false,"reserved":"2026-11-13T01:20:38.540Z","published":"2026-11-13T09:33:38.327Z","modified":"2026-11-13T17:58:50.637Z"}],"publishers":[{"name":"VulnCheck","role":"CNA","organizationId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","modified":"2026-11-13T09:33:38.327Z"},{"name":"CISA-ADP","role":"ADP","organizationId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","modified":"2026-11-13T17:58:50.637Z"}],"references":[{"url":"https://github.com/exceljs/exceljs","tags":["product"],"source":"VulnCheck"},{"url":"https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-pwgq-2cgg-6ph9","tags":["third-party-advisory"],"source":"VulnCheck"},{"url":"https://github.com/exceljs/exceljs/blob/v4.4.0/lib/utils/cell-matrix.js#L50-L52","tags":["technical-description"],"source":"VulnCheck"},{"url":"https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/defined-names.js#L182-L193","tags":["technical-description"],"source":"VulnCheck"},{"url":"https://www.vulncheck.com/advisories/exceljs-through-4.4.0-prototype-pollution-via-proto-defined-name","tags":["third-party-advisory"],"source":"VulnCheck"}],"weaknesses":[{"id":"CWE-1321","description":"Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')","source":"VulnCheck"}],"applicability":[{"source":"VulnCheck","statements":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:exceljs_project:exceljs:*:*:*:*:*:*:*:*","versionEndIncluding":"4.4.0"}]}]}]}],"prioritization":[{"source":"CISA-ADP","type":"SSVC","role":"CISA Coordinator","timestamp":"2026-11-13T17:58:33.563826Z","decisions":[{"name":"Exploitation","value":"none"},{"name":"Automatable","value":"no"},{"name":"Technical Impact","value":"partial"}]}]},"title":"ExcelJS through 4.4.0 Prototype Pollution via __proto__ Defined Name","titleSource":"VulnCheck","descriptionSource":"VulnCheck","description":"ExcelJS through 4.4.0 contains a prototype pollution vulnerability that allows attackers to add numeric keys to Object.prototype through a crafted defined name referencing a __proto__ sheet. Attackers can supply an xlsx whose xl/workbook.xml definedName range targets __proto__, causing CellMatrix to write empty arrays onto Object.prototype process-wide when workbook.xlsx.load() runs.","score":6.3,"severity":"medium","published":"2026-11-13T09:33:38.327Z","modified":"2026-11-13T17:58:50.637Z","withdrawn":false,"knownExploited":false,"affected":[],"products":[{"vendor":"exceljs","name":"exceljs","platforms":[],"versions":[{"version":"0","status":"affected","lessThanOrEqual":"4.4.0","versionType":"semver"}],"defaultStatus":"unaffected","packageURL":"pkg:npm/exceljs","packageIdentity":{"ecosystem":"npm","name":"exceljs"},"cpes":[],"source":"VulnCheck","url":"https://www.cve.org/CVERecord?id=CVE-2026-128336"}],"remediation":[],"references":["https://github.com/exceljs/exceljs","https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-pwgq-2cgg-6ph9","https://github.com/exceljs/exceljs/blob/v4.4.0/lib/utils/cell-matrix.js#L50-L52","https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/defined-names.js#L182-L193","https://www.vulncheck.com/advisories/exceljs-through-4.4.0-prototype-pollution-via-proto-defined-name"],"sources":[{"name":"CVE","id":"CVE-2026-128336","modified":"2026-11-13T17:58:50.637Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-128336"}],"assessments":[{"source":"VulnCheck","vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","score":6.3},{"source":"VulnCheck","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L","score":4.8}],"sourceAffected":[],"observedAt":"2026-11-13T19:45:16.750Z","kev":{"status":"not-listed","checkedAt":"2026-11-15T00:25:34.584Z"},"coverage":[{"source":"NVD","status":"refresh-failed","attemptedAt":"2026-11-14T01:35:32.178Z"},{"source":"GHSA","status":"available","checkedAt":"2026-11-14T01:25:33.862Z","attemptedAt":"2026-11-14T01:25:33.862Z"},{"source":"EUVD","status":"available","checkedAt":"2026-11-14T01:25:32.248Z","attemptedAt":"2026-11-14T01:25:32.248Z"},{"source":"EPSS","status":"available","checkedAt":"2026-11-14T01:25:32.245Z","attemptedAt":"2026-11-14T01:25:32.245Z"}],"evidence":[{"source":"ENISA EUVD","id":"EUVD-2026-125041","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-125041","modified":"Nov 13, 2026, 5:58:50 PM","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","checkedAt":"2026-11-14T01:25:32.248Z"},{"source":"FIRST EPSS","id":"CVE-2026-128336","url":"https://www.first.org/epss/","probability":0.00425,"percentile":0.37312,"date":"2026-11-13","checkedAt":"2026-11-14T01:25:32.245Z"},{"source":"GitHub Advisory Database","id":"GHSA-3wrp-r2q4-573c","url":"https://github.com/advisories/GHSA-3wrp-r2q4-573c","modified":"2026-11-13T12:31:48Z","score":4.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L","checkedAt":"2026-11-14T01:25:33.862Z"}],"aiSummary":{"text":"ExcelJS through 4.4.0 has a prototype pollution vulnerability via __proto__ defined name, allowing attackers to add numeric keys to Object.prototype. Attackers can supply a crafted xlsx file to achieve this. The impact is writing empty arrays onto Object.prototype process-wide.","model":"@cf/meta/llama-3.3-70b-instruct-fp8-fast","generatedAt":"2026-11-14T01:01:04.014Z","sources":[{"name":"CVE","url":"https://www.cve.org/CVERecord?id=CVE-2026-128336"}]}}