Red Hat Product Errata RHSA-2026:65764 - Security Advisory Issued: 2026-09-09 Updated: 2026-09-09 RHSA-2026:65764 - Security Advisory Overview Updated Packages Synopsis Important: thunderbird security update Type/Severity Security Advisory: Important Red Hat Lightspeed patch analysis Identify and remediate systems affected by this advisory. View affected systems Topic An update for thunderbird is now available for Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.4 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. Description 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. Solution For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Affected Products Red Hat Enterprise Linux for x86_64 - Extended Life Cycle Long Life 8.4 x86_64 Red Hat Enterprise Linux Server - AUS 8.4 x86_64 Fixes BZ - 2517820 - CVE-2026-74934 firefox: thunderbird: Site isolation issue in the Graphics: CanvasWebGL component BZ - 2517822 - CVE-2026-74953 firefox: thunderbird: Privilege escalation in the Networking: Cookies component BZ - 2517823 - CVE-2026-74987 firefox: thunderbird: Internally found bugs fixed in Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154 BZ - 2517825 - CVE-2026-74948 firefox: thunderbird: Information disclosure in the Graphics component BZ - 2517831 - CVE-2026-74971 firefox: thunderbird: Information disclosure in the DOM: UI Events & Focus Handling component BZ - 2517833 - CVE-2026-74941 firefox: thunderbird: Privilege escalation in the Graphics: CanvasWebGL component BZ - 2517834 - CVE-2026-74965 firefox: Privilege escalation in the Shell Integration component BZ - 2517835 - CVE-2026-74946 firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component BZ - 2517836 - CVE-2026-74973 firefox: Race condition, use-after-free in the Graphics component BZ - 2517839 - CVE-2026-74990 firefox: thunderbird: Internally found bugs fixed in Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154 BZ - 2517841 - CVE-2026-74940 firefox: thunderbird: Use-after-free in the Graphics: Text component BZ - 2517845 - CVE-2026-74960 firefox: thunderbird: Site isolation issue in the WebExtensions component BZ - 2517849 - CVE-2026-74959 firefox: thunderbird: Mitigation bypass in the Storage: Cache API component BZ - 2517851 - CVE-2026-74976 firefox: thunderbird: JIT miscompilation in the JavaScript Engine: JIT component BZ - 2517853 - CVE-2026-74974 firefox: thunderbird: Same-origin policy bypass in the Graphics: ImageLib component BZ - 2517856 - CVE-2026-74957 firefox: thunderbird: Mitigation bypass in the Safe Browsing component BZ - 2517858 - CVE-2026-74967 firefox: thunderbird: Same-origin policy bypass in the Audio/Video: Playback component BZ - 2517859 - CVE-2026-74942 firefox: Privilege escalation in the Remote Settings Client component BZ - 2517860 - CVE-2026-74939 firefox: thunderbird: Privilege escalation in the DOM: Navigation component BZ - 2517862 - CVE-2026-74972 firefox: thunderbird: Information disclosure in the DOM: Push Subscriptions component BZ - 2517863 - CVE-2026-74945 firefox: thunderbird: Information disclosure in the Graphics: Text component BZ - 2517866 - CVE-2026-74963 firefox: thunderbird: Same-origin policy bypass in the Networking: Cookies component BZ - 2517870 - CVE-2026-74964 firefox: Integer overflow in the Graphics component BZ - 2517872 - CVE-2026-74962 firefox: Site isolation issue in the Networking: Cookies component BZ - 2517874 - CVE-2026-74935 firefox: thunderbird: Privilege escalation in the DOM: Networking component CVEs CVE-2026-74934 CVE-2026-74935 CVE-2026-74939 CVE-2026-74940 CVE-2026-74941 CVE-2026-74942 CVE-2026-74945 CVE-2026-74946 CVE-2026-74948 CVE-2026-74953 CVE-2026-74957 CVE-2026-74959 CVE-2026-74960 CVE-2026-74962 CVE-2026-74963 CVE-2026-74964 CVE-2026-74965 CVE-2026-74967 CVE-2026-74971 CVE-2026-74972 CVE-2026-74973 CVE-2026-74974 CVE-2026-74976 CVE-2026-74987 CVE-2026-74990 References https://access.redhat.com/security/updates/classification/#important Note: More recent versions of these packages may be available. Click a package name for more details. Red Hat Enterprise Linux for x86_64 - Extended Life Cycle Long Life 8.4 SRPM thunderbird-140.14.0-1.el8_4.src.rpm SHA-256: 5d9a7d12b461484bd5602d4a2c39413d8b7a525e471b1e03984ad24c67dd2343 x86_64 thunderbird-140.14.0-1.el8_4.x86_64.rpm SHA-256: 2e803e0c90c5dc28f04ed962e85a0c552f13be78c8072a0021be5adfb64a93b5 thunderbird-debuginfo-140.14.0-1.el8_4.x86_64.rpm SHA-256: b47503f335b10139f4e95be0ea4c0d40bdd96a127374287e7c6966aa4fc47156 thunderbird-debugsource-140.14.0-1.el8_4.x86_64.rpm SHA-256: 3d2cbf5ccf84d83251b6614623972645b2a7fed1db91f95fe3d559a6550d38ce Red Hat Enterprise Linux Server - AUS 8.4 SRPM thunderbird-140.14.0-1.el8_4.src.rpm SHA-256: 5d9a7d12b461484bd5602d4a2c39413d8b7a525e471b1e03984ad24c67dd2343 x86_64 thunderbird-140.14.0-1.el8_4.x86_64.rpm SHA-256: 2e803e0c90c5dc28f04ed962e85a0c552f13be78c8072a0021be5adfb64a93b5 thunderbird-debuginfo-140.14.0-1.el8_4.x86_64.rpm SHA-256: b47503f335b10139f4e95be0ea4c0d40bdd96a127374287e7c6966aa4fc47156 thunderbird-debugsource-140.14.0-1.el8_4.x86_64.rpm SHA-256: 3d2cbf5ccf84d83251b6614623972645b2a7fed1db91f95fe3d559a6550d38ce The Red Hat security contact is secalert@redhat.com . More contact details at https://access.redhat.com/security/team/contact/ .