CVE-2026-6763: Mitigation bypass in the File Handling component

Published Apr 21, 2026
·
Updated

Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Affected Software

7 affected componentsFixes available
Mozilla Firefox ESR<140.10
140.10
Mozilla Firefox<150
150
Mozilla Thunderbird<150
150
Mozilla Thunderbird<140.10
140.10
Mozilla Firefox<140.10.0
Mozilla Firefox<150.0
Mozilla Thunderbird>=140.0<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 140.10
  2. Upgrade

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

    Fixed in 150
  3. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 150
  4. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 140.10
  5. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 150
  6. Upgrade

    Upgrade Thunderbird 140.10 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·02:02 PM
DescriptionSeverityAffected Software

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-2026-6763?

CVE-2026-6763 has been categorized as a moderate severity vulnerability.

2

How do I fix CVE-2026-6763?

To fix CVE-2026-6763, update to Mozilla Firefox 150, Firefox ESR 140.10, Thunderbird 150, or Thunderbird 140.10.

3

Which products are affected by CVE-2026-6763?

CVE-2026-6763 affects Firefox versions below 150, Firefox ESR versions below 140.10, and Thunderbird versions below 150 and 140.10.

4

Is there a workaround for CVE-2026-6763?

There are no specific workarounds for CVE-2026-6763; the recommended action is to apply the updates.

5

When was CVE-2026-6763 disclosed?

CVE-2026-6763 was disclosed as part of a security advisory by Mozilla.

Company

Resources

Contact

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