Sandbox Escape in Firefox CanvasWebGL Due to Boundary Error

Publication date: 2026-01-13

Last updated on: 2026-06-30

Assigner: Mozilla Corporation

Description

Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-01-13

Last Modified

2026-06-30

Generated

2026-07-06

AI Q&A

2026-01-14

EPSS Evaluated

2026-07-05

NVD

CVE-2026-0878

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 147 (exc)
mozilla	firefox_esr	to 140.7 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-20	The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
CWE-119	The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Attack-Flow Graph

Executive Summary

This vulnerability is a sandbox escape caused by incorrect boundary conditions in the Graphics: CanvasWebGL component of Firefox. It affects Firefox versions before 147 and Firefox ESR versions before 140.7. Essentially, it allows an attacker to break out of the browser's sandbox environment, potentially enabling unauthorized code execution or actions beyond the intended security restrictions.

Impact Analysis

The vulnerability can allow attackers to escape the browser's sandbox, which is designed to isolate web content and prevent malicious code from affecting the user's system. This can lead to unauthorized code execution or actions within the browser environment, potentially compromising user data or system security.

Mitigation Strategies

To mitigate this vulnerability, update Firefox to version 147 or later, or Firefox ESR to version 140.7 or later, as these versions include fixes addressing this sandbox escape vulnerability. [2]

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