{"id":"CVE-2026-78207","aliases":[],"cve":{"records":[{"id":"CVE-2026-78207","source":"VulnCheck","state":"PUBLISHED","reasons":[],"replacements":[],"disputed":false,"unsupportedWhenAssigned":false,"reserved":"2026-08-24T00:15:01.656Z","published":"2026-08-24T00:30:47.125Z","modified":"2026-11-08T14:09:03.861Z"}],"publishers":[{"name":"VulnCheck","role":"CNA","organizationId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","modified":"2026-11-08T14:09:03.861Z"},{"name":"CISA-ADP","role":"ADP","organizationId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","modified":"2026-08-24T17:46:59.464Z"}],"references":[{"url":"https://github.com/exceljs/exceljs","tags":["product"],"source":"VulnCheck"},{"url":"https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-qwr4-7h29-chpf","tags":["third-party-advisory","vendor-advisory"],"source":"VulnCheck"},{"url":"https://github.com/exceljs/exceljs/blob/v4.4.0/lib/utils/under-dash.js#L155-L181","tags":["technical-description"],"source":"VulnCheck"},{"url":"https://www.vulncheck.com/advisories/exceljs-through-prototype-pollution-via-deepmerge-reached-from-note-serialization","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":"2026-08-24T17:45:28.866234Z","decisions":[{"name":"Exploitation","value":"none"},{"name":"Automatable","value":"yes"},{"name":"Technical Impact","value":"total"}]}]},"title":"exceljs through 4.4.0 Prototype Pollution via deepMerge Reached From Note Serialization","titleSource":"VulnCheck","descriptionSource":"VulnCheck","description":"exceljs through 4.4.0 contains a prototype pollution vulnerability in the deepMerge helper that fails to reject __proto__, constructor, or prototype keys when merging note objects. Attackers can assign parsed JSON with a malicious __proto__ property to cell notes, modifying Object.prototype and affecting all plain objects created in the process.","score":9.4,"severity":"critical","published":"2026-08-24T00:30:47.125Z","modified":"2026-11-08T14:09:03.861Z","withdrawn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-2026-78207"}],"remediation":[],"references":["https://github.com/exceljs/exceljs","https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-qwr4-7h29-chpf","https://github.com/exceljs/exceljs/blob/v4.4.0/lib/utils/under-dash.js#L155-L181","https://www.vulncheck.com/advisories/exceljs-through-prototype-pollution-via-deepmerge-reached-from-note-serialization"],"sources":[{"name":"CVE","id":"CVE-2026-78207","modified":"2026-11-08T14:09:03.861Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-78207"}],"assessments":[{"source":"VulnCheck","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N","score":9.3},{"source":"VulnCheck","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L","score":9.4}],"sourceAffected":[],"observedAt":"2026-11-08T14:31:51.218Z","kev":{"status":"not-listed","checkedAt":"2026-11-15T00:20:33.177Z"},"coverage":[{"source":"NVD","status":"available","checkedAt":"2026-11-08T15:05:36.836Z","attemptedAt":"2026-11-08T15:05:36.836Z"},{"source":"GHSA","status":"available","checkedAt":"2026-11-08T15:05:37.277Z","attemptedAt":"2026-11-08T15:05:37.277Z"},{"source":"EUVD","status":"available","checkedAt":"2026-11-08T15:05:37.377Z","attemptedAt":"2026-11-08T15:05:37.377Z"},{"source":"EPSS","status":"available","checkedAt":"2026-11-08T15:05:36.892Z","attemptedAt":"2026-11-08T15:05:36.892Z"}],"evidence":[{"source":"NVD","id":"CVE-2026-78207","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-78207","modified":"2026-10-14T13:10:00.187","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","checkedAt":"2026-11-08T15:05:36.836Z"},{"source":"NVD","id":"CVE-2026-78207","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-78207","modified":"2026-10-14T13:10:00.187","score":9.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L","checkedAt":"2026-11-08T15:05:36.836Z"},{"source":"FIRST EPSS","id":"CVE-2026-78207","url":"https://www.first.org/epss/","probability":0.00603,"percentile":0.49116,"date":"2026-11-08","checkedAt":"2026-11-08T15:05:36.892Z"},{"source":"GitHub Advisory Database","id":"GHSA-3cpv-r8x3-29fp","url":"https://github.com/advisories/GHSA-3cpv-r8x3-29fp","modified":"2026-08-24T03:31:14Z","score":9.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L","checkedAt":"2026-11-08T15:05:37.277Z"},{"source":"ENISA EUVD","id":"EUVD-2026-64682","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-64682","modified":"Nov 8, 2026, 2:09:03 PM","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N","checkedAt":"2026-11-08T15:05:37.377Z"}],"aiSummary":{"text":"exceljs through 4.4.0 has a prototype pollution vulnerability via deepMerge, allowing attackers to modify Object.prototype by assigning malicious JSON to cell notes. This affects all plain objects created in the process. The vulnerability is due to the deepMerge helper not rejecting __proto__, constructor, or prototype keys.","model":"@cf/meta/llama-3.3-70b-instruct-fp8-fast","generatedAt":"2026-11-08T14:41:09.681Z","sources":[{"name":"CVE","url":"https://www.cve.org/CVERecord?id=CVE-2026-78207"}]}}