CVE-2026-84126

Analyzed Analyzed - Analysis Complete

Incorrect Boundary Conditions in Firefox Layout Grid Component

Publication date: 2026-09-01

Last updated on: 2026-09-03

Assigner: Mozilla Corporation

Description

Incorrect boundary conditions in the Layout: Grid component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-01

Last Modified

2026-09-03

Generated

2026-09-22

AI Q&A

2026-09-01

EPSS Evaluated

2026-09-20

NVD

CVE-2026-84126

EUVD

EUVD-2026-69075

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 155.0.0 (exc)
mozilla	thunderbird	to 155.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-120	The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

Attack-Flow Graph

Executive Summary

This vulnerability involves incorrect boundary conditions in the Layout: Grid component of Firefox. It was patched in Firefox version 155. The issue likely allows unexpected behavior or crashes due to improper handling of grid layout boundaries.

Detection Guidance

This vulnerability is specific to Firefox 155's Layout: Grid component. Detection requires checking Firefox version and inspecting for grid layout rendering issues. Use commands like 'firefox --version' to verify version and 'about:support' in Firefox to check component details.

Impact Analysis

If exploited, this flaw could cause Firefox to crash or behave unpredictably when rendering grid layouts. Users might experience application instability or denial of service when visiting maliciously crafted web pages.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or other common standards and regulations. The issue is limited to incorrect boundary conditions in the Layout: Grid component of Firefox and Thunderbird, which could lead to minor information disclosure but does not involve unauthorized data access or processing violations typical of compliance breaches.

Mitigation Strategies

Update Firefox to version 155 or later to address the incorrect boundary conditions in the Layout: Grid component.

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