CVE-2026-74976

Analyzed Analyzed - Analysis Complete

JIT Miscompilation in Firefox JavaScript Engine

Publication date: 2026-08-18

Last updated on: 2026-08-19

Assigner: Mozilla Corporation

Description

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-18

Last Modified

2026-08-19

Generated

2026-09-08

AI Q&A

2026-08-18

EPSS Evaluated

2026-09-07

NVD

CVE-2026-74976

EUVD

EUVD-2026-60670

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	From 141.0 (inc) to 153.1.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.1.0 (exc)
mozilla	thunderbird	to 140.14.0 (exc)
mozilla	firefox	to 140.14.0 (exc)

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 Firefox's JavaScript Engine. It occurs when the Just-In-Time compiler incorrectly translates JavaScript code, potentially leading to memory corruption or arbitrary code execution. The issue was patched in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

Detection Guidance

This vulnerability is specific to Firefox and Firefox ESR versions affected by JIT miscompilation. Detection involves checking installed versions of Firefox or Firefox ESR against the fixed versions (Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1). Use commands like 'firefox --version' or 'firefox-esr --version' to check versions. If versions are below the fixed releases, the system is vulnerable.

Impact Analysis

If exploited, this vulnerability could allow attackers to execute arbitrary code on your system, crash the browser, or bypass security mechanisms. Users running unpatched versions of Firefox or Firefox ESR are at risk.

Compliance Impact

The provided CVE data does not specify how this vulnerability impacts compliance with standards like GDPR or HIPAA. The description only mentions a JIT miscompilation issue in Firefox without details on data exposure or regulatory implications.

Mitigation Strategies

Update Firefox to version 154 or later, Firefox ESR to version 140.14 or later, or Firefox ESR to version 153.1 or later to address the JIT miscompilation vulnerability.

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