CVE-2026-84121
critical · 9.6Sandbox 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.
9.6
CVSS
0.3%
EPSS (exploit prob.)
25th
EPSS percentile
2026-09-01
Published
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Weaknesses
CWE-416
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| mozilla | firefox | < 115.40.0 |
| mozilla | firefox | >= 116.0, < 140.15.0 |
| mozilla | firefox | >= 141.0.0, < 153.2.0 |
| mozilla | firefox | >= 154.0.0, < 155.0.0 |
| mozilla | thunderbird | < 140.15.0 |
| mozilla | thunderbird | >= 141.0, < 153.2.0 |
| mozilla | thunderbird | >= 154.0, < 155.0 |
Check a specific version with /api/v1/cve/match.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2059018
- https://www.mozilla.org/security/advisories/mfsa2026-82/
- https://www.mozilla.org/security/advisories/mfsa2026-83/
- https://www.mozilla.org/security/advisories/mfsa2026-84/
- https://www.mozilla.org/security/advisories/mfsa2026-85/
- https://www.mozilla.org/security/advisories/mfsa2026-86/
- https://www.mozilla.org/security/advisories/mfsa2026-87/
- https://www.mozilla.org/security/advisories/mfsa2026-88/
Query this programmatically:
curl https://evil-db.io/api/v1/cve/CVE-2026-84121