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Critical 9.6Published Sep 1, 2026
CVE-2026-84121Sandbox escape due to use-after-free in the DOM: Security component
Updated under an hour ago ()
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It affects Mozilla Firefox and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 9.6 CRITICAL (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
- Weakness (CWE)
- CWE-416
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- mozilla
- NVD analysis
- Analyzed
- Record last updated
- Sep 2, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Mozilla Firefox mozilla:firefox (from the name) | 115.40 builds before 115.* not affected; 140.15 builds before 140.* not affected; 153.2 builds before 153.* not affected; from 155 not affected | CNA record |
Mozilla Thunderbird mozilla:thunderbird (from the name) | 140.15 builds before 140.* not affected; 153.2 builds before 153.* not affected; from 155 not affected | CNA record |
mozilla firefox mozilla:firefox | before 115.40.0; from 116.0 before 140.15.0; from 141.0.0 before 153.2.0; from 154.0.0 before 155.0.0 | NVD |
mozilla thunderbird mozilla:thunderbird | before 140.15.0; from 141.0 before 153.2.0; from 154.0 before 155.0 | NVD |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2059018permissions-required
- https://www.mozilla.org/security/advisories/mfsa2026-82/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-83/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-84/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-85/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-86/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-87/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-88/vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.