CVE-2026-84118
Received Received - Intake

Use-After-Free in Firefox JavaScript GC

Publication date: 2026-09-01

Last updated on: 2026-09-01

Assigner: Mozilla Corporation

Description
Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 155 and Firefox ESR 153.2.

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Meta Information

Published
2026-09-01
Last Modified
2026-09-01
Generated
2026-09-01
AI Q&A
2026-09-01
EPSS Evaluated
N/A
NVD
CVE-2026-84118
EUVD
EUVD-2026-69070

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
mozilla firefox to 155 (inc)
mozilla firefox_esr to 153.2 (inc)
mozilla firefox 155
mozilla firefox_esr 153.2

Helpful Resources

Exploitability

CWE
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

CVE-2026-84118 is a use-after-free vulnerability in Firefox's JavaScript garbage collection component. This flaw occurs when the program attempts to use memory that has already been freed, potentially leading to memory corruption or arbitrary code execution.

Detection Guidance

Detecting this vulnerability requires checking the installed version of Firefox or Firefox ESR. On Linux or macOS, run: firefox --version or firefox-esr --version. On Windows, check the application properties. If the version is below 155 for Firefox or 153.2 for ESR, the system is vulnerable.

Impact Analysis

Attackers could exploit this vulnerability to execute malicious code, crash the browser, or gain unauthorized access to your system. Successful exploitation may allow them to install malware, steal data, or take control of your device.

Compliance Impact

This vulnerability could lead to data breaches, which may violate GDPR's data protection requirements or HIPAA's safeguards for protected health information. Organizations using vulnerable Firefox versions may face compliance penalties and reputational damage.

Mitigation Strategies

Immediately update Firefox to version 155 or Firefox ESR to version 153.2. Disable JavaScript if updates are not possible, as this vulnerability is tied to the JavaScript: GC component. Monitor for unusual system behavior or crashes that may indicate exploitation attempts.

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