CVE-2026-100776: Use-after-free in the JavaScript: WebAssembly component

Published Sep 29, 2026
·
Updated

Use-after-free in the JavaScript: WebAssembly 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>=140.0.0<140.17.0
Mozilla Firefox>=153.0.0<153.4.0
Mozilla Firefox>=154.0.0<157.0.0
Mozilla Thunderbird>=140.0<140.17.0
Mozilla Thunderbird>=153.0<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~deb12u1153.6.0esr-1~deb13u1153.5.1esr-1153.7.0esr-1
debian/thunderbird<=1:140.12.0esr-1~deb12u1, <=1:140.12.0esr-1~deb13u1
1:153.6.0esr-1~deb12u21:153.6.0esr-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 153.6.0esr-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 1:153.6.0esr-1~deb12u2Fixed in 1:153.6.0esr-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·01:00 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

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