CVE-2026-4720
Last modified
CVE-2026-4720 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. EPSS estimates a 0.42% chance of exploitation in the next 30 days.
Description
Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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 | < 140.9.0 |
| Mozilla | Firefox | < 149.0 |
| Mozilla | Thunderbird | < 140.9.0 |
| Mozilla | Thunderbird | < 149.0 |
References
- https://www.mozilla.org/security/advisories/mfsa2026-20/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-22/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-23/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-24/Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2026-4720?
How severe is CVE-2026-4720?
How do I fix CVE-2026-4720?
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.
Related CVEs from 2026
- CVE-2026-47194Frappe is a full-stack web application framework. Prior to 1…8.6
- CVE-2026-47195Quest Bot is an opensource Discord Bot. Prior to version 1.1…7.1
- CVE-2026-47196Quest Bot is an opensource Discord Bot. Prior to version 1.1…8.4
- CVE-2026-47197Quest Bot is an opensource Discord Bot. Prior to version 1.1…7.2
- CVE-2026-47198Paymenter is a free and open-source webshop solution for man…8.5
- CVE-2026-47199Frappe is a full-stack web application framework. Prior to 1…2.3
- CVE-2026-47200Nuxt is an open-source web development framework for Vue.js.…5.3
- CVE-2026-47201authentik is an open-source identity provider. Prior to vers…8.5
- CVE-2026-47202Kavita is a cross platform reading server. Prior to 0.9.0.2,…9.3
- CVE-2026-47203Authelia is an open-source authentication and authorization …2.9
- CVE-2026-47204Envoy is an open source edge and service proxy designed for …7.5
- CVE-2026-47205Envoy is an open source edge and service proxy designed for …5.9
Are you affected by CVE-2026-4720?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST