Buffer overflow in Mozilla Firefox
CVE-2026-2778
Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Vulnerability class: Buffer Overflow
EPSS: 0.005 (38.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.
Affected products
- Mozilla Firefox — versions 115.33, 140.8, 148
- Mozilla Thunderbird — versions 140.8, 148
Weakness classification (CWE)
References
- security@mozilla.org (Permissions Required, Issue Tracking)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- 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-2026-2778?
- CVE-2026-2778 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 10.0/10. Published 2026-02-24.
- How severe is CVE-2026-2778?
- Critical severity. CVSS v3 base score is 10.0 out of 10.