CVE-2026-109740: Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component

Published Oct 13, 2026
·
Updated

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5.

Other sources

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

— NVD

Affected Software

4 affected componentsFixes available
Mozilla Firefox<158
158
Mozilla Firefox ESR<153.5
153.5
Mozilla Thunderbird<153.5
153.5
Mozilla Thunderbird<158
158

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 158
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 153.5
  3. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 158
  4. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 153.5
  5. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 158
  6. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 153.5

Event History

Oct 13, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·12:29 PM
Data Sourced
via MITRE·12:29 PM
Description
Data Sourced
via NVD·01:17 PM
Description

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

Which Firefox releases contain the fix?

The issue was fixed in Firefox 158 and Firefox ESR 153.5.

Company

Resources

Contact

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