CVE-2026-6754

Modified Modified - Updated After Analysis

Use-After-Free in Firefox JavaScript Engine Enables Exploits

Publication date: 2026-04-21

Last updated on: 2026-06-30

Assigner: Mozilla Corporation

Description

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-04-21

Last Modified

2026-06-30

Generated

2026-07-06

AI Q&A

2026-04-21

EPSS Evaluated

2026-07-05

NVD

CVE-2026-6754

EUVD

EUVD-2026-24095

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 150.0 (exc)
mozilla	firefox	to 115.35.0 (exc)
mozilla	firefox	From 140.0 (inc) to 140.10.0 (exc)
mozilla	thunderbird	to 140.10.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-825	The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.
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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 issue in the JavaScript Engine component of Mozilla Firefox. A use-after-free vulnerability occurs when a program continues to use a pointer after the memory it points to has been freed, which can lead to unexpected behavior or exploitation.

The issue was addressed and fixed in Firefox version 150, Firefox ESR 115.35, and Firefox ESR 140.10.

Impact Analysis

Exploitation of a use-after-free vulnerability in the JavaScript Engine could potentially allow an attacker to execute arbitrary code, cause a crash, or manipulate the behavior of the browser. This could lead to unauthorized actions or compromise of the system running the affected Firefox versions.

Mitigation Strategies

To mitigate this use-after-free vulnerability in the JavaScript Engine component, update your Firefox browsers to the fixed versions: Firefox 150, Firefox ESR 115.35, or Firefox ESR 140.10.

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