CVE-2026-109733

Deferred Deferred - Pending Action

JIT Miscompilation in Firefox JavaScript Engine

Publication date: 2026-10-13

Last updated on: 2026-10-15

Assigner: Mozilla Corporation

Description

JIT miscompilation 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.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-10-13

Last Modified

2026-10-15

Generated

2026-10-19

AI Q&A

2026-10-13

EPSS Evaluated

2026-10-18

NVD

CVE-2026-109733

EUVD

EUVD-2026-98650

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	158
mozilla	firefox	esr

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-843	The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

Attack-Flow Graph

Executive Summary

This is a JIT miscompilation vulnerability in the JavaScript Engine. It occurs when the Just-In-Time compiler incorrectly translates JavaScript code, leading to potential memory corruption or arbitrary code execution. It was fixed in Firefox 158 and specific Firefox ESR versions.

Detection Guidance

This vulnerability is specific to Firefox versions before 158, ESR 115.43, and ESR 153.5. Detection involves checking installed Firefox versions. Use commands like 'firefox --version' or 'apt list --installed | grep firefox' (Linux) to verify. If outdated, update immediately.

Impact Analysis

An attacker could exploit this to execute arbitrary code on your system, potentially leading to data theft, system compromise, or installation of malware. Users of affected Firefox versions are at risk until they update.

Compliance Impact

The provided CVE data does not specify direct impacts on compliance with standards like GDPR or HIPAA. The vulnerability involves JIT miscompilation in the JavaScript Engine, which could potentially lead to arbitrary code execution or data corruption. However, no explicit compliance implications are mentioned in the context.

Mitigation Strategies

Update Firefox to version 158 or later, Firefox ESR 115.43 or later, or Firefox ESR 153.5 or later to address the JIT miscompilation vulnerability.

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