CVE-2026-109757

Deferred Deferred - Pending Action

Firefox Race Condition Sandbox Escape

Publication date: 2026-10-13

Last updated on: 2026-10-15

Assigner: Mozilla Corporation

Description

Sandbox escape due to race condition in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-10-13

Last Modified

2026-10-15

Generated

2026-10-19

AI Q&A

2026-10-13

EPSS Evaluated

2026-10-18

NVD

CVE-2026-109757

EUVD

EUVD-2026-98518

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 158 (inc)
mozilla	firefox_esr	to 153.5 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-362	The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Attack-Flow Graph

Executive Summary

This is a sandbox escape vulnerability caused by a race condition in Firefox's Networking component. A race condition occurs when two or more threads access shared data simultaneously, leading to unexpected behavior. In this case, it allows malicious code to break out of the browser's sandbox, potentially gaining unauthorized access to the host system.

Impact Analysis

If exploited, this vulnerability could allow attackers to run arbitrary code on your system outside the browser's security sandbox. This could lead to data theft, installation of malware, or further compromise of your device. Users of affected Firefox versions are at risk if they visit malicious websites.

Compliance Impact

This vulnerability is a sandbox escape due to a race condition in the Networking component of Firefox. Such escapes could potentially allow unauthorized access to system resources, which may impact data confidentiality and integrity. However, the provided CVE data does not specify direct implications for compliance with standards like GDPR or HIPAA.

Mitigation Strategies

Update Firefox to version 158 or later and Firefox ESR to version 153.5 or later to address the sandbox escape vulnerability.

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