CVE-2026-2777
CRITICALCVSS 9.8/10EPSS 0.37%
Last modified
CVE-2026-2777 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Privilege escalation in the Messaging System 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 0.37% chance of exploitation in the next 30 days.
Description
Privilege escalation in the Messaging System 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:U/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=2015305Issue 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-2026-2777?
Privilege escalation in the Messaging System 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-2026-2777?
CVE-2026-2777 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.37% probability of exploitation in the next 30 days.
How do I fix CVE-2026-2777?
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-2026-2777?
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