RHSA-2026:65757 — Security Advisory

An update for thunderbird is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On.

Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

• firefox: thunderbird: Site isolation issue in the Graphics: CanvasWebGL component (CVE-2026-74934)

• firefox: thunderbird: Privilege escalation in the Networking: Cookies component (CVE-2026-74953)

• firefox: thunderbird: Internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154 (CVE-2026-74987)

• firefox: thunderbird: Information disclosure in the Graphics component (CVE-2026-74948)

• firefox: thunderbird: Information disclosure in the DOM: UI Events & Focus Handling component (CVE-2026-74971)

• firefox: thunderbird: Privilege escalation in the Graphics: CanvasWebGL component (CVE-2026-74941)

• firefox: Privilege escalation in the Shell Integration component (CVE-2026-74965)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-74946)

• firefox: Race condition, use-after-free in the Graphics component (CVE-2026-74973)

• firefox: thunderbird: Internally found bugs fixed in Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154 (CVE-2026-74990)

• firefox: thunderbird: Use-after-free in the Graphics: Text component (CVE-2026-74940)

• firefox: thunderbird: Site isolation issue in the WebExtensions component (CVE-2026-74960)

• firefox: thunderbird: Mitigation bypass in the Storage: Cache API component (CVE-2026-74959)

• firefox: thunderbird: JIT miscompilation in the JavaScript Engine: JIT component (CVE-2026-74976)

• firefox: thunderbird: Same-origin policy bypass in the Graphics: ImageLib component (CVE-2026-74974)

• firefox: thunderbird: Mitigation bypass in the Safe Browsing component (CVE-2026-74957)

• firefox: thunderbird: Same-origin policy bypass in the Audio/Video: Playback component (CVE-2026-74967)

• firefox: Privilege escalation in the Remote Settings Client component (CVE-2026-74942)

• firefox: thunderbird: Privilege escalation in the DOM: Navigation component (CVE-2026-74939)

• firefox: thunderbird: Information disclosure in the DOM: Push Subscriptions component (CVE-2026-74972)

• firefox: thunderbird: Information disclosure in the Graphics: Text component (CVE-2026-74945)

• firefox: thunderbird: Same-origin policy bypass in the Networking: Cookies component (CVE-2026-74963)

• firefox: Integer overflow in the Graphics component (CVE-2026-74964)

• firefox: Site isolation issue in the Networking: Cookies component (CVE-2026-74962)

• firefox: thunderbird: Privilege escalation in the DOM: Networking component (CVE-2026-74935)

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.