CVE-2026-109729
Received Received - Intake

Use-After-Free in Firefox JavaScript Engine

Publication date: 2026-10-13

Last updated on: 2026-10-13

Assigner: Mozilla Corporation

Description
Use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

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Meta Information

Published
2026-10-13
Last Modified
2026-10-13
Generated
2026-10-19
AI Q&A
2026-10-13
EPSS Evaluated
2026-10-18
NVD
CVE-2026-109729
EUVD
EUVD-2026-98647

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
mozilla firefox to 158 (inc)
mozilla firefox_esr to 115.43 (inc)
mozilla firefox_esr to 153.5 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

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Executive Summary

This is a use-after-free vulnerability in the JavaScript Engine's JIT component. Use-after-free means the software tries to use memory after it has been freed, which can lead to crashes or arbitrary code execution.

Detection Guidance

Detection requires checking Firefox version against patched releases. For Firefox, run: about:support in the browser and check version under Application Basics. For system-wide checks, use package managers like apt list --installed | grep firefox or rpm -qa | grep firefox on Linux. Compare versions against Firefox 158, Firefox ESR 115.43, or Firefox ESR 153.5.

Impact Analysis

An attacker could exploit this to execute malicious code on your system, potentially taking control of your device or stealing data. It may also cause crashes in Firefox.

Compliance Impact

This vulnerability is a use-after-free in the JavaScript Engine JIT component, which could allow for memory corruption and potential arbitrary code execution. Such vulnerabilities may lead to unauthorized data access or modification, which could violate GDPR's data protection requirements or HIPAA's safeguards for protected health information if exploited.

Mitigation Strategies

Update Firefox to version 158 or later, Firefox ESR to version 115.43 or later, or Firefox ESR to version 153.5 or later to address the use-after-free vulnerability in the JavaScript Engine JIT component.

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