CVE-2026-100819

Analyzed Analyzed - Analysis Complete

XPCOM Boundary Condition Sandbox Escape in Firefox

Publication date: 2026-09-29

Last updated on: 2026-10-05

Assigner: Mozilla Corporation

Description

Sandbox escape due to incorrect boundary conditions in the XPCOM component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

CVSS 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-2026-100819

EUVD

EUVD-2026-88798

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	to 115.42.0 (exc)
mozilla	firefox	From 116.0 (inc) to 140.17.0 (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)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
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 allows an attacker to escape the sandbox due to incorrect boundary conditions in the XPCOM component of Firefox. This means malicious code could run outside the restricted environment, potentially gaining higher system privileges.

Detection Guidance

This vulnerability is specific to Firefox and related products. Detection involves checking the installed version of Firefox against the patched versions (Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, Firefox ESR 140.17). Use commands like 'firefox --version' or check the package manager for updates.

Impact Analysis

If exploited, this vulnerability could allow an attacker to execute arbitrary code on your system, leading to data theft, malware installation, or unauthorized access. Users of affected Firefox versions are at risk until they update to the patched versions.

Compliance Impact

This vulnerability allows sandbox escape, potentially enabling unauthorized access to sensitive data. This could violate GDPR's data protection requirements or HIPAA's safeguards for protected health information if exploited.

Mitigation Strategies

Update Firefox to a patched version: Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, or Firefox ESR 140.17 or later. Disable XPCOM components if not required.

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