Red Hat Product Errata RHSA-2026:26539 - Security Advisory Issued: 2026-06-17 Updated: 2026-06-17 RHSA-2026:26539 - 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 10.0 Extended Update Support. 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: 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. 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 Update Support 10.0 x86_64 Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 10.0 s390x Red Hat Enterprise Linux for Power, little endian - Extended Update Support 10.0 ppc64le Red Hat Enterprise Linux for ARM 64 - Extended Update Support 10.0 aarch64 Red Hat Enterprise Linux for ARM 64 - 4 years of updates 10.0 aarch64 Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 10.0 s390x Red Hat Enterprise Linux for Power, little endian - 4 years of support 10.0 ppc64le Red Hat Enterprise Linux for x86_64 - 4 years of updates 10.0 x86_64 Fixes BZ - 2476469 - CVE-2026-8388 firefox: thunderbird: Incorrect boundary conditions in the JavaScript Engine: JIT component BZ - 2476475 - CVE-2026-8391 firefox: thunderbird: Other issue in the JavaScript Engine component BZ - 2476492 - CVE-2026-8401 firefox: thunderbird: Sandbox escape in the Profile Backup component BZ - 2479839 - CVE-2026-8956 firefox: Integer overflow in the Networking: JAR component BZ - 2479840 - CVE-2026-8975 firefox: Memory safety bugs fixed in Firefox ESR 115.36, Firefox ESR 140.11 and Firefox 151 BZ - 2479842 - CVE-2026-8955 firefox: thunderbird: Privilege escalation in the DOM: Workers component BZ - 2479846 - CVE-2026-8968 firefox: Denial-of-service due to invalid pointer in the Audio/Video: Web Codecs component BZ - 2479847 - CVE-2026-8954 firefox: Incorrect boundary conditions, integer overflow in the Audio/Video component BZ - 2479848 - CVE-2026-8958 firefox: Information disclosure, sandbox escape in the Security: Process Sandboxing component BZ - 2479849 - CVE-2026-8946 firefox: thunderbird: Incorrect boundary conditions in the Audio/Video: Web Codecs component BZ - 2479852 - CVE-2026-8970 firefox: Privilege escalation in the Security component BZ - 2479853 - CVE-2026-8950 firefox: Same-origin policy bypass in the Networking: HTTP component BZ - 2479855 - CVE-2026-8974 firefox: Memory safety bugs fixed in Firefox ESR 140.11 and Firefox 151 BZ - 2479860 - CVE-2026-8953 firefox: Sandbox escape due to use-after-free in the Disability Access APIs component BZ - 2479861 - CVE-2026-8959 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component BZ - 2479871 - CVE-2026-8961 firefox: Spoofing issue in the Form Autofill component BZ - 2479873 - CVE-2026-8947 firefox: thunderbird: Use-after-free in the DOM: Bindings (WebIDL) component BZ - 2479876 - CVE-2026-8962 firefox: Mitigation bypass in the DOM: Security component BZ - 2479880 - CVE-2026-8957 firefox: Privilege escalation in the Enterprise Policies component CVEs CVE-2026-8388 CVE-2026-8391 CVE-2026-8401 CVE-2026-8946 CVE-2026-8947 CVE-2026-8950 CVE-2026-8953 CVE-2026-8954 CVE-2026-8955 CVE-2026-8956 CVE-2026-8957 CVE-2026-8958 CVE-2026-8959 CVE-2026-8961 CVE-2026-8962 CVE-2026-8968 CVE-2026-8970 CVE-2026-8974 CVE-2026-8975 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 Update Support 10.0 SRPM thunderbird-140.11.0-1.el10_0.src.rpm SHA-256: d5bb605817f782d5001902d3ca6c98666949eab2b1882e9bc40f0b7525428155 x86_64 thunderbird-140.11.0-1.el10_0.x86_64.rpm SHA-256: 90edba2c8d14f027dfad05cc7b8810fc63aa6dc37e82567867336208269c075c thunderbird-debuginfo-140.11.0-1.el10_0.x86_64.rpm SHA-256: ca7e7b1f8bf0d163ed90cad2a0c05474130f2a418116f4bfd5ef65d04fd23f29 thunderbird-debugsource-140.11.0-1.el10_0.x86_64.rpm SHA-256: bcbaceba812a661a508f26c07603e1ecac2710e428cb3fae4091bd616b2d670f Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 10.0 SRPM thunderbird-140.11.0-1.el10_0.src.rpm SHA-256: d5bb605817f782d5001902d3ca6c98666949eab2b1882e9bc40f0b7525428155 s390x thunderbird-140.11.0-1.el10_0.s390x.rpm SHA-256: 54f1c64eca2b972dd2bf500a18606e35e1e12f94031244d547530a88d61fc369 thunderbird-debuginfo-140.11.0-1.el10_0.s390x.rpm SHA-256: 67d7b8ba589dd4650eb8b3a14edbee63343e2cee37f0c0baa6079c455fb41451 thunderbird-debugsource-140.11.0-1.el10_0.s390x.rpm SHA-256: 2e42e63c27cc2135e2abd4133bf38797b070a916a34236dbf7c218c029063312 Red Hat Enterprise Linux for Power, little endian - Extended Update Support 10.0 SRPM thunderbird-140.11.0-1.el10_0.src.rpm SHA-256: d5bb605817f782d5001902d3ca6c98666949eab2b1882e9bc40f0b7525428155 ppc64le thunderbird-140.11.0-1.el10_0.ppc64le.rpm SHA-256: 6c6f5e08adfb201a3bbccfc782ddd6be208244ff68c13216349b73547d7b04db thunderbird-debuginfo-140.11.0-1.el10_0.ppc64le.rpm SHA-256: c364545fe66d6dfc41c97a7cfb5b1e729d72a00a2a83c52a7387436a761cc513 thunderbird-debugsource-140.11.0-1.el10_0.ppc64le.rpm SHA-256: f96d463defcd37d9178eab09ed34f53a308dcc497437b8682b9198e3b7e28782 Red Hat Enterprise Linux for ARM 64 - Extended Update Support 10.0 SRPM thunderbird-140.11.0-1.el10_0.src.rpm SHA-256: d5bb605817f782d5001902d3ca6c98666949eab2b1882e9bc40f0b7525428155 aarch64 thunderbird-140.11.0-1.el10_0.aarch64.rpm SHA-256: 175df0f92f720fb159239fdbc4498f397dfe3fd7c021e4bdad511ac4920f7662 thunderbird-debuginfo-140.11.0-1.el10_0.aarch64.rpm SHA-256: b4fd280c1383be862f369319ee77ec7fa96896f549d820e8d7512d700d0b984f thunderbird-debugsource-140.11.0-1.el10_0.aarch64.rpm SHA-256: bb0740d5461347ab5a3fc64ee1ff79e68f8d7ad8c5b2ce75f8e0ec1584596d4e Red Hat Enterprise Linux for ARM 64 - 4 years of updates 10.0 SRPM thunderbird-140.11.0-1.el10_0.src.rpm SHA-256: d5bb605817f782d5001902d3ca6c98666949eab2b1882e9bc40f0b7525428155 aarch64 thunderbird-140.11.0-1.el10_0.aarch64.rpm SHA-256: 175df0f92f720fb159239fdbc4498f397dfe3fd7c021e4bdad511ac4920f7662 thunderbird-debuginfo-140.11.0-1.el10_0.aarch64.rpm SHA-256: b4fd280c1383be862f369319ee77ec7fa96896f549d820e8d7512d700d0b984f thunderbird-debugsource-140.11.0-1.el10_0.aarch64.rpm SHA-256: bb0740d5461347ab5a3fc64ee1ff79e68f8d7ad8c5b2ce75f8e0ec1584596d4e Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 10.0 SRPM thunderbird-140.11.0-1.el10_0.src.rpm SHA-256: d5bb605817f782d5001902d3ca6c98666949eab2b1882e9bc40f0b7525428155 s390x thunderbird-140.11.0-1.el10_0.s390x.rpm SHA-256: 54f1c64eca2b972dd2bf500a18606e35e1e12f94031244d547530a88d61fc369 thunderbird-debuginfo-140.11.0-1.el10_0.s390x.rpm SHA-256: 67d7b8ba589dd4650eb8b3a14edbee63343e2cee37f0c0baa6079c455fb41451 thunderbird-debugsource-140.11.0-1.el10_0.s390x.rpm SHA-256: 2e42e63c27cc2135e2abd4133bf38797b070a916a34236dbf7c218c029063312 Red Hat Enterprise Linux for Power, little endian - 4 years of support 10.0 SRPM thunderbird-140.11.0-1.el10_0.src.rpm SHA-256: d5bb605817f782d5001902d3ca6c98666949eab2b1882e9bc40f0b7525428155 ppc64le thunderbird-140.11.0-1.el10_0.ppc64le.rpm SHA-256: 6c6f5e08adfb201a3bbccfc782ddd6be208244ff68c13216349b73547d7b04db thunderbird-debuginfo-140.11.0-1.el10_0.ppc64le.rpm SHA-256: c364545fe66d6dfc41c97a7cfb5b1e729d72a00a2a83c52a7387436a761cc513 thunderbird-debugsource-140.11.0-1.el10_0.ppc64le.rpm SHA-256: f96d463defcd37d9178eab09ed34f53a308dcc497437b8682b9198e3b7e28782 Red Hat Enterprise Linux for x86_64 - 4 years of updates 10.0 SRPM thunderbird-140.11.0-1.el10_