CVE-2026-109776

Deferred Deferred - Pending Action

Race Condition in Firefox XPCOM Component

Publication date: 2026-10-13

Last updated on: 2026-10-15

Assigner: Mozilla Corporation

Description

Race condition in the XPCOM 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-2026-109776

EUVD

EUVD-2026-98536

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 158 (inc)
mozilla	firefox_esr	to 153.5 (inc)
mozilla	firefox	From 158 (inc)
mozilla	firefox_esr	From 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 race condition vulnerability in the XPCOM component of Firefox. A race condition occurs when the behavior of a program depends on the sequence or timing of uncontrollable events, which can lead to unexpected results. The issue was addressed in Firefox 158 and Firefox ESR 153.5.

Detection Guidance

Detecting this race condition vulnerability requires checking the installed Firefox version. Run 'firefox --version' or 'firefox-esr --version' to verify if the version is below 158 or 153.5 respectively.

Impact Analysis

A race condition could allow an attacker to manipulate the timing of events to gain unauthorized access, execute malicious code, or cause system instability. This might lead to data breaches, system compromise, or other security issues depending on the attacker's goals.

Compliance Impact

The provided CVE data does not specify how this race condition vulnerability in Firefox affects compliance with standards like GDPR or HIPAA. Without additional context on data exposure or processing impacts, it is unclear how this issue would influence regulatory compliance.

Mitigation Strategies

Update Firefox to version 158 or later and Firefox ESR to version 153.5 or later immediately. Use your system's package manager or download directly from Mozilla's website.

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