CVE-2026-2778
CRITICALCVSS 10/10EPSS 0.48%
Last modified
CVE-2026-2778 is a critical-severity vulnerability rated 10/10 on the CVSS scale. 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.. EPSS estimates a 0.48% chance of exploitation in the next 30 days.
Description
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 115.33.0 |
| Mozilla | Firefox | < 148.0 |
| Mozilla | Firefox | >= 128.0, < 140.8.0 |
| Mozilla | Thunderbird | < 140.8.0 |
| Mozilla | Thunderbird | < 148.0 |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2016358Issue Tracking, Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-13/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-14/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-15/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-16/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-17/Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is 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.
How severe is CVE-2026-2778?
CVE-2026-2778 has a CVSS score of 10/10 (CRITICAL severity). The EPSS model estimates a 0.48% probability of exploitation in the next 30 days.
How do I fix CVE-2026-2778?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2026-2778?
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