CVE-2026-100811

Analyzed Analyzed - Analysis Complete

Use-After-Free Sandbox Escape in Firefox

Publication date: 2026-09-29

Last updated on: 2026-10-05

Assigner: Mozilla Corporation

Description

Sandbox escape due to use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.

CVSS Scores

EPSS Scores

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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-2026-100811

EUVD

EUVD-2026-88790

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	From 154.0.0 (inc) to 157.0.0 (exc)
mozilla	thunderbird	From 154.0 (inc) to 157.0 (exc)
mozilla	firefox	From 141.0 (inc) to 153.4.0 (exc)
mozilla	thunderbird	to 140.17.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.4.0 (exc)
mozilla	firefox	to 140.17.0 (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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 sandbox escape vulnerability caused by a use-after-free issue in the DOM Core and HTML components of Firefox. It allows an attacker to break out of the browser's sandbox, potentially gaining access to the host system.

Detection Guidance

Detection of this vulnerability requires checking the installed version of Firefox ESR or Firefox against the fixed versions (Firefox ESR 153.4, Firefox 157, Firefox ESR 140.17). Use package managers or browser update tools to verify the current version.

Impact Analysis

If exploited, this vulnerability could allow malicious code to run outside the browser's sandbox, potentially leading to unauthorized access to system resources, data theft, or installation of malware on your device.

Compliance Impact

This vulnerability could lead to data breaches, which may violate GDPR and HIPAA compliance requirements. Organizations using affected Firefox versions may face legal penalties, reputational damage, and loss of customer trust.

Mitigation Strategies

Update Firefox ESR to version 153.4 or later and Firefox to version 157 or later to address the use-after-free vulnerability in the DOM: Core & HTML component.

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