{"id":"CVE-2026-84121","published":"2026-09-01T12:18:41Z","modified":"2026-09-02T03:55:38Z","title":"Sandbox escape due to use-after-free in the DOM: Security component","vendor":"Mozilla","product":"Firefox","tier":"tail","description":{"text":"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.","provenance":"source","from":"CVE.org"},"cvss":{"score":9.6,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H","provenance":"source","from":"CISA ADP Vulnrichment"},"epss":{"score":0.00319,"percentile":0.24815,"provenance":"source"},"cwes":[{"id":"CWE-416","name":"Use After Free"}],"references":[{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=2059018","tags":[]},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-82/","tags":[]},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-83/","tags":[]},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-84/","tags":[]},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-85/","tags":[]},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-86/","tags":[]},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-87/","tags":[]},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-88/","tags":[]}],"priority":{"score":11.7,"factors":[{"name":"EPSS percentile","points":4.96},{"name":"CVSS severity","points":6.72}]},"vendorSlug":"mozilla","euvd":{"id":"EUVD-2026-69066","exploited":false,"provenance":"source"},"lineage":{"familyId":"fam-class-mozilla-firefox-cwe-416"}}