{"apiVersion":"1.0","identifier":"CVE-2026-78207","description":"exceljs-hardened before 5.0.0 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.","publishedAt":"2026-08-24T01:16:58","lastModifiedAt":"2026-08-24T18:17:30","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-78207","cvssScore":9.4,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L","epssProbability":0.00439,"riskScore":0.98,"affectedProduct":"exceljs-hardened","affectedVersions":"<5.0.0","vulnerabilityType":"Library","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-78207","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-78207","en":"https://www.redsauce.net/en/cves/CVE-2026-78207","fr":"https://www.redsauce.net/fr/cves/CVE-2026-78207","pt":"https://www.redsauce.net/pt/cves/CVE-2026-78207","de":"https://www.redsauce.net/de/cves/CVE-2026-78207","sk":"https://www.redsauce.net/sk/cves/CVE-2026-78207","el":"https://www.redsauce.net/el/cves/CVE-2026-78207"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-78207"}}