CVE-2026-84125

Analyzed Analyzed - Analysis Complete

Use-after-free in Firefox DOM Core & HTML

Publication date: 2026-09-01

Last updated on: 2026-09-02

Assigner: Mozilla Corporation

Description

Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, 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-2026-84125

EUVD

EUVD-2026-69074

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 153.2.0 (exc)
mozilla	firefox	From 154.0.0 (inc) to 155.0.0 (exc)
mozilla	thunderbird	to 153.2.0 (exc)
mozilla	thunderbird	From 154.0 (inc) to 155.0 (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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 DOM: Core & HTML component. It occurs when a program tries to use memory after it has been freed, potentially leading to crashes or arbitrary code execution.

Detection Guidance

Detection requires checking Firefox version. Run 'firefox --version' or check 'about:support' in Firefox. Versions before 155 or Firefox ESR before 153.2 are vulnerable.

Impact Analysis

An attacker could exploit this to crash your browser or run malicious code on your system. It may allow unauthorized access to sensitive data or system resources if not patched.

Compliance Impact

This vulnerability involves a use-after-free issue in Firefox's DOM and HTML components, which could lead to memory corruption or arbitrary code execution. Such flaws may compromise data confidentiality and integrity, potentially violating GDPR's security requirements (Article 32) and HIPAA's safeguards for protected health information. Organizations using affected Firefox versions may face compliance risks if exploitation results in unauthorized data access or processing.

Mitigation Strategies

Update Firefox to version 155 or later and Firefox ESR to 153.2 or later. Disable automatic updates temporarily if needed until patches are applied.

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