Use-After-Free in Firefox JavaScript Engine Enables Exploits

Publication date: 2026-01-13

Last updated on: 2026-04-13

Assigner: Mozilla Corporation

Description

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-01-13

Last Modified

2026-04-13

Generated

2026-07-06

AI Q&A

2026-01-14

EPSS Evaluated

2026-07-05

NVD

CVE-2026-0884

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 147 (exc)
mozilla	firefox_esr	to 140.7 (exc)

Helpful Resources

Exploitability

CWE

KEV

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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Attack-Flow Graph

Executive Summary

This vulnerability is a use-after-free bug in the JavaScript Engine component of Firefox versions prior to 147 and Firefox ESR versions prior to 140.7. A use-after-free occurs when a program continues to use memory after it has been freed, which can lead to unexpected behavior or exploitation by attackers.

Impact Analysis

The vulnerability has a high impact with a CVSS score of 9.8, meaning it can be exploited remotely without user interaction to cause high confidentiality, integrity, and availability impacts. This could allow attackers to execute arbitrary code, take control of the affected system, or cause crashes and denial of service.

Mitigation Strategies

To mitigate this vulnerability, update Firefox to version 147 or later, or Firefox ESR to version 140.7 or later, as these versions include fixes for the use-after-free vulnerability in the JavaScript Engine component. [2]

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