CVE-2026-109761: Use-after-free in the JavaScript: WebAssembly component

Published Oct 13, 2026
·
Updated

Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.

Affected Software

2 affected componentsFixes available
Mozilla Firefox<158
158
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 Firefox to a version that resolves this vulnerability.

    Fixed in 158
  3. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 158

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
DescriptionSeverityWeakness

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

Which Firefox versions are affected?

The issue was fixed in Firefox 158. The provided information does not identify the first affected version or whether any Firefox release channels are excluded.

2

What must an attacker do to exploit this issue?

The provided information identifies the affected component as JavaScript: WebAssembly, but does not specify the delivery method, required user interaction, or other exploitation prerequisites.

3

How can I determine whether I need to remediate this vulnerability?

Check the Firefox version deployed in your environment. Firefox 158 contains the fix; the provided information does not establish the status of versions earlier than 158 beyond indicating that the vulnerability was fixed in that release.

Company

Resources

Contact

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