Use After Free in Mozilla Firefox
CVE-2026-4684
Race condition, use-after-free in the Graphics: WebRender component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Vulnerability class: Race Condition
EPSS: 0.004 (27.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
Affected products
- Mozilla Firefox — versions 115.34, 140.9, 149
- Mozilla Thunderbird — versions 140.9, 149
Weakness classification (CWE)
References
- security@mozilla.org (Permissions Required)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org
- security@mozilla.org
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-4684?
- CVE-2026-4684 is a high-severity vulnerability in Mozilla Firefox, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.5/10. Published 2026-03-24.
- How severe is CVE-2026-4684?
- High severity. CVSS v3 base score is 7.5 out of 10.