CVE-2026-100787

Analyzed Analyzed - Analysis Complete

XUL Sandbox Escape in Firefox ESR and Firefox

Publication date: 2026-09-29

Last updated on: 2026-10-05

Assigner: Mozilla Corporation

Description

Sandbox escape in the XUL component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-29

Last Modified

2026-10-05

Generated

2026-10-19

AI Q&A

2026-09-29

EPSS Evaluated

2026-10-18

NVD

CVE-2026-100787

EUVD

EUVD-2026-88939

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 153.4.0 (exc)
mozilla	firefox	From 154.0.0 (inc) to 157.0.0 (exc)
mozilla	thunderbird	to 153.4.0 (exc)
mozilla	thunderbird	From 154.0 (inc) to 157.0 (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.

Attack-Flow Graph

Executive Summary

This is a sandbox escape vulnerability in the XUL component of Firefox. It allows malicious code to break out of the browser's security sandbox, potentially gaining unauthorized access to the host system.

Detection Guidance

This vulnerability is specific to Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157. Detection involves checking installed versions of these applications. Use commands like 'firefox --version' or 'thunderbird --version' to verify if vulnerable versions are running.

Impact Analysis

If exploited, this vulnerability could allow attackers to execute arbitrary code on your system with the same privileges as your user account. This could lead to data theft, malware installation, or unauthorized system access.

Compliance Impact

The provided CVE data does not specify how this vulnerability affects compliance with standards like GDPR or HIPAA. Without additional context on data exposure or processing impacts, no direct compliance implications can be determined.

Mitigation Strategies

Update Firefox ESR to version 153.4 or Firefox to version 157 or later to address the sandbox escape vulnerability in the XUL component.

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