CVE-2026-6754: Use-after-free in the JavaScript Engine component

Published Apr 21, 2026
·
Updated

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Affected Software

9 affected componentsFixes available
Mozilla Firefox ESR<115.35
115.35
Mozilla Firefox ESR<140.10
140.10
Mozilla Firefox<150
150
Mozilla Thunderbird<150
150
Mozilla Thunderbird<140.10
140.10
Mozilla Firefox<115.35.0
Mozilla Firefox<150.0
Mozilla Firefox>=140.0<140.10.0
Mozilla Thunderbird<140.10.0

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 115.35
  2. Upgrade

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

    Fixed in 140.10
  3. Upgrade

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

    Fixed in 150
  4. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 150
  5. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 115.35
  6. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 140.10
  7. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 150
  8. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 140.10

Event History

Apr 21, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
Updated
via Mozilla·12:00 AM
Affected Software
CVE Published
via MITRE·12:40 PM
Data Sourced
via MITRE·12:40 PM
Description
Data Sourced
via NVD·01:16 PM
DescriptionSeverityWeaknessAffected Software
Data Sourced
via Red Hat·02:01 PM
DescriptionSeverityAffected Software
May 2, 58290
Event
via FIRST·04:48 AM

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is the severity of CVE-2026-6754?

CVE-2026-6754 has a high severity rating due to the potential exploitation of the use-after-free vulnerability in the JavaScript Engine.

2

How do I fix CVE-2026-6754?

To fix CVE-2026-6754, update your Mozilla Firefox or Thunderbird to version 150 or the respective ESR versions 115.35 and 140.10.

3

Which products are affected by CVE-2026-6754?

CVE-2026-6754 affects Mozilla Firefox versions prior to 150, Thunderbird versions prior to 150, and Firefox ESR versions prior to 115.35 and 140.10.

4

What are the potential impacts of CVE-2026-6754?

The exploitation of CVE-2026-6754 could potentially allow an attacker to execute arbitrary code or cause crashes.

5

Is CVE-2026-6754 related to any specific components?

CVE-2026-6754 specifically pertains to a use-after-free vulnerability within the JavaScript Engine component.

Company

Resources

Contact

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