{"id":"CVE-2026-84121","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-84121","generatedAt":"2026-10-28T10:35:46.566Z","title":"Sandbox escape due to use-after-free in the DOM: Security component.","description":"Sandbox escape due to use-after-free in the DOM: Security component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.","published":"2026-09-01T13:20:06.000Z","lastModified":"2026-09-02T16:36:20.000Z","status":"Analyzed","sourceIdentifier":"security@mozilla.org","cvss":{"version":"3.1","score":9.6,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H"},"cwe":["CWE-416"],"affected":["mozilla/firefox","mozilla/thunderbird"],"epss":{"score":0.00319,"percentile":0.24744,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.32%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=2059018","tags":["Permissions Required"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-82/","tags":["Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-83/","tags":["Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-84/","tags":["Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-85/","tags":["Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-86/","tags":["Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-87/","tags":["Vendor Advisory"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-88/","tags":["Vendor Advisory"],"source":"security@mozilla.org"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-84121","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}