Red Hat Product Errata RHSA-2026:21381 - Security Advisory Issued: 2026-05-27 Updated: 2026-05-27 RHSA-2026:21381 - 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 9. 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 9 x86_64 Red Hat Enterprise Linux for x86_64 - Extended Update Support 9.8 x86_64 Red Hat Enterprise Linux for IBM z Systems 9 s390x Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 9.8 s390x Red Hat Enterprise Linux for Power, little endian 9 ppc64le Red Hat Enterprise Linux for Power, little endian - Extended Update Support 9.8 ppc64le Red Hat Enterprise Linux for ARM 64 9 aarch64 Red Hat Enterprise Linux for ARM 64 - Extended Update Support 9.8 aarch64 Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 9.8 ppc64le Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 9.8 x86_64 Red Hat Enterprise Linux for ARM 64 - 4 years of updates 9.8 aarch64 Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 9.8 s390x Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 9.8 x86_64 Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 9.8 aarch64 Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 9.8 ppc64le Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 9.8 s390x Fixes BZ - 2476469 - CVE-2026-8388 firefox: Incorrect boundary conditions in the JavaScript Engine: JIT component BZ - 2476475 - CVE-2026-8391 firefox: Other issue in the JavaScript Engine component BZ - 2476492 - CVE-2026-8401 firefox: 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: 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: 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: 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: 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 9 SRPM thunderbird-140.11.0-1.el9_8.src.rpm SHA-256: a20b3594d8b9295b159a654f83095f27a1e4472db37f37a8811df14f7482faff x86_64 thunderbird-140.11.0-1.el9_8.x86_64.rpm SHA-256: a4533fc61a365e2ee40138ee8d693212138f324436d39f304a421040586ad34c thunderbird-debuginfo-140.11.0-1.el9_8.x86_64.rpm SHA-256: d102e59d9e9a4d6764be1220cc55b43c274ab25f9d45ae2b0991d8220818d3dd thunderbird-debugsource-140.11.0-1.el9_8.x86_64.rpm SHA-256: 9347ac6d6be9dd68bd4aecd103ed351078587476325fd32062c5e8526d18e28a Red Hat Enterprise Linux for x86_64 - Extended Update Support 9.8 SRPM thunderbird-140.11.0-1.el9_8.src.rpm SHA-256: a20b3594d8b9295b159a654f83095f27a1e4472db37f37a8811df14f7482faff x86_64 thunderbird-140.11.0-1.el9_8.x86_64.rpm SHA-256: a4533fc61a365e2ee40138ee8d693212138f324436d39f304a421040586ad34c thunderbird-debuginfo-140.11.0-1.el9_8.x86_64.rpm SHA-256: d102e59d9e9a4d6764be1220cc55b43c274ab25f9d45ae2b0991d8220818d3dd thunderbird-debugsource-140.11.0-1.el9_8.x86_64.rpm SHA-256: 9347ac6d6be9dd68bd4aecd103ed351078587476325fd32062c5e8526d18e28a Red Hat Enterprise Linux for IBM z Systems 9 SRPM thunderbird-140.11.0-1.el9_8.src.rpm SHA-256: a20b3594d8b9295b159a654f83095f27a1e4472db37f37a8811df14f7482faff s390x thunderbird-140.11.0-1.el9_8.s390x.rpm SHA-256: 8525204d0b8744dc138ca96a0065b8b68eaebde304152b70a72979105bada8a7 thunderbird-debuginfo-140.11.0-1.el9_8.s390x.rpm SHA-256: bbbcc1c4ed2fcd78ea4c7b85946f9237ef06a2ac59d18e91897de5cca791b542 thunderbird-debugsource-140.11.0-1.el9_8.s390x.rpm SHA-256: 73150f77917d4efbbc061a96a0ed4bef3ab84a6496a9eeae3f2a83d3d12258f2 Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 9.8 SRPM thunderbird-140.11.0-1.el9_8.src.rpm SHA-256: a20b3594d8b9295b159a654f83095f27a1e4472db37f37a8811df14f7482faff s390x thunderbird-140.11.0-1.el9_8.s390x.rpm SHA-256: 8525204d0b8744dc138ca96a0065b8b68eaebde304152b70a72979105bada8a7 thunderbird-debuginfo-140.11.0-1.el9_8.s390x.rpm SHA-256: bbbcc1c4ed2fcd78ea4c7b85946f9237ef06a2ac59d18e91897de5cca791b542 thunderbird-debugsource-140.11.0-1.el9_8.s390x.rpm SHA-256: 73150f77917d4efbbc061a96a0ed4bef3ab84a6496a9eeae3f2a83d3d12258f2 Red Hat Enterprise Linux for Power, little endian 9 SRPM thunderbird-140.11.0-1.el9_8.src.rpm SHA-256: a20b3594d8b9295b159a654f83095f27a1e4472db37f37a8811df14f7482faff ppc64le thunderbird-140.11.0-1.el9_8.ppc64le.rpm SHA-256: 32dbb77d61ee311d087d8580d7920396e8ab31b31461d304faccd1e4252a8e11 thunderbird-debuginfo-140.11.0-1.el9_8.ppc64le.rpm SHA-256: ed27e3420225738b8023e4cf17529731bfbed3aadd2cc8084979303be5ae41b3 thunderbird-debugsource-140.11.0-1.el9_8.ppc64le.rpm SHA-256: 80df5c3fcb76250d806bf5bf389e004a0a7c56819ee2827924220edfac89dfaf Red Hat Enterprise Linux for Power, little endian - Extended Update Support 9.8 SRPM thunderbird-140.11.0-1.el9_8.src.rpm SHA-256: a20b3594d8b9295b159a654f83095f27a1e4472db37f37a8811df14f7482faff ppc64le thunderbird-140.11.0-1.el9_8.ppc64le.rpm SHA-256: 32dbb77d61ee311d087d8580d7920396e8ab31b31461d304faccd1e4252a8e11 thunderbird-debuginfo-140.11.0-1.el9_8.ppc64le.rpm SHA-256: ed27e3420225738b8023e4cf17529731bfbed3aadd2cc8084979303be5ae41b3 thunderbird-debugsource-140.11.0-1.el9_8.ppc64le.rpm SHA-256: 80df5c3fcb76250d806bf5bf389e004a0a7c56819ee2827924220edfac89dfaf Red Hat Enterprise Linux for ARM 64 9 SRPM thunderbird-140.11.0-1.el9_8.src.rpm SHA-256: a20b3594d8b9295b159a654f83095f27a1e4472db37f37a8811df14f7482faff aarch64 thunderbird-140.11.0-1.el9_8.aarch64.rpm SHA-256: c5f20cfa4b6bf5a382293213d251be7b46188892bbdb2adde8cf3c142e5ea23f thunderbird-debuginfo-140.11.0-1.el9_8.aarch64.rpm SHA-256: c2377066545c645f45ad2e81