RLSA-2026:21381

Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

• firefox: Incorrect boundary conditions in the JavaScript Engine: JIT component (CVE-2026-8388)

• firefox: Other issue in the JavaScript Engine component (CVE-2026-8391)

• firefox: Sandbox escape in the Profile Backup component (CVE-2026-8401)

• firefox: Integer overflow in the Networking: JAR component (CVE-2026-8956)

• firefox: Memory safety bugs fixed in Firefox ESR 115.36, Firefox ESR 140.11 and Firefox 151 (CVE-2026-8975)

• firefox: Privilege escalation in the DOM: Workers component (CVE-2026-8955)

• firefox: Denial-of-service due to invalid pointer in the Audio/Video: Web Codecs component (CVE-2026-8968)

• firefox: Incorrect boundary conditions, integer overflow in the Audio/Video component (CVE-2026-8954)

• firefox: Information disclosure, sandbox escape in the Security: Process Sandboxing component (CVE-2026-8958)

• firefox: Incorrect boundary conditions in the Audio/Video: Web Codecs component (CVE-2026-8946)

• firefox: Privilege escalation in the Security component (CVE-2026-8970)

• firefox: Same-origin policy bypass in the Networking: HTTP component (CVE-2026-8950)

• firefox: Memory safety bugs fixed in Firefox ESR 140.11 and Firefox 151 (CVE-2026-8974)

• firefox: Sandbox escape due to use-after-free in the Disability Access APIs component (CVE-2026-8953)

• firefox: Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component (CVE-2026-8959)

• firefox: Spoofing issue in the Form Autofill component (CVE-2026-8961)

• firefox: Use-after-free in the DOM: Bindings (WebIDL) component (CVE-2026-8947)

• firefox: Mitigation bypass in the DOM: Security component (CVE-2026-8962)

• firefox: Privilege escalation in the Enterprise Policies component (CVE-2026-8957)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.