CVE-2026-84121
⛔ criticalSummary
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 Score
9.6
Critical
EPSS Score
0.3
Exploit Probability
Published Date
2026-09-01
First Seen: 2026-09-03
📊 Relative Risk Intelligence
This CVE is Very High Risk - more severe than 90.2% of all 360,548 vulnerabilities in our database.
#35,421
Top 10% most severe
Severity Percentile
🎯 CISA SSVC Assessment Updated: Sep 1, 2026
🔍 Exploitation Status
None
No known exploits
⚙️ Automatable
NO
Requires human interaction
💥 Technical Impact
Total
Complete system compromise possible
🏆 Discovered By
Yaqoub Aldurayhim
SSVC data provided by
CISA
Last Modified
2026-09-02
Source
NVD 🔗
CVSS Vector 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
CWE IDs (Weakness Types)