CVE-2026-109721
MEDIUMCVSS 5.4/10EPSS 0.25%
Last modified
CVE-2026-109721 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. Incorrect boundary conditions in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.. EPSS estimates a 0.25% chance of exploitation in the next 30 days.
Description
Incorrect boundary conditions in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Metrics
Weakness Enumeration
Affected Software
Source: CNA advisory (CVE.org). NVD analysis pending.
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | All versions |
| Mozilla | Thunderbird | All versions |
References
Timeline
- Published
- Last Modified
- Status
- Deferred
Frequently Asked Questions
What is CVE-2026-109721?
Incorrect boundary conditions in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
How severe is CVE-2026-109721?
CVE-2026-109721 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.25% probability of exploitation in the next 30 days.
How do I fix CVE-2026-109721?
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.
Related CVEs from 2026
- CVE-2026-109716Incorrect boundary conditions in the JavaScript Engine compo…8.1
- CVE-2026-109717Use-after-free in the DOM: Bindings (WebIDL) component. This…5.4
- CVE-2026-109718Use-after-free in the XML component. This vulnerability was …5.4
- CVE-2026-109719Race condition, use-after-free in the Graphics: CanvasWebGL …4.2
- CVE-2026-10972Use after free in Ozone in Google Chrome on Linux prior to 1…9.6
- CVE-2026-109720JIT miscompilation in the JavaScript: WebAssembly component.…7.1
- CVE-2026-109722JIT miscompilation in the JavaScript Engine: JIT component. …8.1
- CVE-2026-109723Integer overflow in the Layout: Text and Fonts component. Th…5.4
- CVE-2026-109724Use-after-free in the DOM: Core & HTML component. This vulne…5.4
- CVE-2026-109725Use-after-free in the DOM: Core & HTML component. This vulne…5.4
- CVE-2026-109726Use-after-free in the SVG component. This vulnerability was …5.4
- CVE-2026-109727Use-after-free in the Audio/Video component. This vulnerabil…5.4
Are you affected by CVE-2026-109721?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST