CVE-2026-100818: Sandbox escape due to use-after-free in the Widget: Gtk component

Published Sep 29, 2026
·
Updated

Sandbox escape due to use-after-free in the Widget: Gtk component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.

Affected Software

15 affected componentsFixes available
Mozilla Firefox ESR<140.17
140.17
Mozilla Thunderbird<157
157
Mozilla Thunderbird<140.17
140.17
Mozilla Firefox<140.17.0
Mozilla Firefox>=141.0<153.4.0
Mozilla Firefox>=154.0.0<157.0.0
Mozilla Thunderbird<140.17.0
Mozilla Thunderbird>=141.0<153.4.0
Mozilla Thunderbird>=154.0<157.0
Mozilla Firefox ESR<153.4
153.4
Mozilla Firefox<157
157
Mozilla Thunderbird<153.4
153.4
debian/firefox
160.0-1
debian/firefox-esr<=140.12.0esr-1~deb12u1, <=140.15.0esr-1~deb13u1
153.7.0esr-1~deb12u1153.7.0esr-1~deb13u1153.5.1esr-1153.7.0esr-1
debian/thunderbird<=1:140.12.0esr-1~deb12u1, <=1:140.12.0esr-1~deb13u1
1:153.7.0esr-1~deb12u11:153.7.0esr-1~deb13u11:153.5.0esr-11:153.7.0esr-1

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 140.17
  2. Upgrade

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

    Fixed in 157
  3. Upgrade

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

    Fixed in 153.4
  4. Upgrade

    Upgrade debian/firefox to a version that resolves this vulnerability.

    Fixed in 160.0-1
  5. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 153.7.0esr-1~deb12u1Fixed in 153.7.0esr-1~deb13u1Fixed in 153.5.1esr-1Fixed in 153.7.0esr-1
  6. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:153.7.0esr-1~deb12u1Fixed in 1:153.7.0esr-1~deb13u1Fixed in 1:153.5.0esr-1Fixed in 1:153.7.0esr-1
  7. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 153.4
  8. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 157
  9. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 140.17
  10. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 157
  11. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 140.17
  12. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 153.4

Event History

Sep 29, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·12:36 PM
Data Sourced
via MITRE·12:36 PM
Description
Data Sourced
via Red Hat·01:05 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·01:17 PM
DescriptionSeverityWeaknessAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Company

Resources

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2026 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203