CVE-2026-84120

Analyzed Analyzed - Analysis Complete

Use-after-free in Firefox Audio/Video Component

Publication date: 2026-09-01

Last updated on: 2026-09-02

Assigner: Mozilla Corporation

Description

Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-01

Last Modified

2026-09-02

Generated

2026-09-21

AI Q&A

2026-09-01

EPSS Evaluated

2026-09-20

NVD

CVE-2026-84120

EUVD

EUVD-2026-69065

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	From 154.0.0 (inc) to 155.0.0 (exc)
mozilla	thunderbird	From 154.0 (inc) to 155.0 (exc)
mozilla	firefox	From 141.0.0 (inc) to 153.2.0 (exc)
mozilla	thunderbird	to 140.15.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.2.0 (exc)
mozilla	firefox	to 115.40.0 (exc)
mozilla	firefox	From 116.0 (inc) to 140.15.0 (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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 is a use-after-free vulnerability in Firefox's Audio/Video component. Use-after-free occurs when a program continues to use memory after it has been freed, potentially leading to crashes or arbitrary code execution.

Detection Guidance

This vulnerability is fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2. Check your Firefox version with 'firefox --version' or 'about:support' in Firefox. If your version is older, update immediately.

Impact Analysis

An attacker could exploit this to crash your browser or run malicious code on your device. This could lead to data theft, system compromise, or installation of malware if you visit a specially crafted website.

Compliance Impact

The vulnerability is a use-after-free in Firefox's Audio/Video component, which could allow attackers to execute arbitrary code or bypass security restrictions. This type of flaw may lead to unauthorized data access or processing, potentially violating GDPR's data protection requirements or HIPAA's safeguards for protected health information if exploited.

Mitigation Strategies

Update Firefox to version 155 or later, Firefox ESR 115.40 or later, Firefox ESR 140.15 or later, or Firefox ESR 153.2 or later to address the use-after-free vulnerability in the Audio/Video component.

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