RHSA-2026:1487 - Security Advisory

Topic

An update for thunderbird is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions, and Red Hat Enterprise Linux 8.6 Telecommunications Update Service.

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: Spoofing issue in the Downloads Panel component (CVE-2025-14327)
• firefox: Use-after-free in the JavaScript: GC component (CVE-2026-0885)
• firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147 (CVE-2026-0891)
• firefox: Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-0878)
• firefox: Use-after-free in the IPC component (CVE-2026-0882)
• firefox: Use-after-free in the JavaScript Engine component (CVE-2026-0884)
• firefox: Information disclosure in the Networking component (CVE-2026-0883)
• firefox: Mitigation bypass in the DOM: Security component (CVE-2026-0877)
• firefox: Spoofing issue in the DOM: Copy & Paste and Drag & Drop component (CVE-2026-0890)
• firefox: Clickjacking issue, information disclosure in the PDF Viewer component (CVE-2026-0887)
• firefox: Sandbox escape due to incorrect boundary conditions in the Graphics component (CVE-2026-0879)
• firefox: Sandbox escape due to integer overflow in the Graphics component (CVE-2026-0880)
• firefox: Incorrect boundary conditions in the Graphics component (CVE-2026-0886)

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 Extension 8.6 x86_64
• Red Hat Enterprise Linux Server - AUS 8.6 x86_64
• Red Hat Enterprise Linux Server - TUS 8.6 x86_64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 8.6 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 8.6 x86_64

Fixes

• BZ - 2420507 - CVE-2025-14327 firefox: Spoofing issue in the Downloads Panel component
• BZ - 2428961 - CVE-2026-0885 firefox: thunderbird: Use-after-free in the JavaScript: GC component
• BZ - 2428963 - CVE-2026-0891 firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147
• BZ - 2428965 - CVE-2026-0878 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component
• BZ - 2428966 - CVE-2026-0882 firefox: thunderbird: Use-after-free in the IPC component
• BZ - 2428967 - CVE-2026-0884 firefox: thunderbird: Use-after-free in the JavaScript Engine component
• BZ - 2428968 - CVE-2026-0883 firefox: thunderbird: Information disclosure in the Networking component
• BZ - 2428969 - CVE-2026-0877 firefox: thunderbird: Mitigation bypass in the DOM: Security component
• BZ - 2428971 - CVE-2026-0890 firefox: thunderbird: Spoofing issue in the DOM: Copy & Paste and Drag & Drop component
• BZ - 2428972 - CVE-2026-0887 firefox: thunderbird: Clickjacking issue, information disclosure in the PDF Viewer component
• BZ - 2428973 - CVE-2026-0879 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Graphics component
• BZ - 2428975 - CVE-2026-0880 firefox: thunderbird: Sandbox escape due to integer overflow in the Graphics component
• BZ - 2428978 - CVE-2026-0886 firefox: thunderbird: Incorrect boundary conditions in the Graphics component

CVEs

• CVE-2025-14327
• CVE-2026-0877
• CVE-2026-0878
• CVE-2026-0879
• CVE-2026-0880
• CVE-2026-0882
• CVE-2026-0883
• CVE-2026-0884
• CVE-2026-0885
• CVE-2026-0886
• CVE-2026-0887
• CVE-2026-0890
• CVE-2026-0891

References

• https://access.redhat.com/security/updates/classification/#important