RHSA-2026:1487 — Security Advisory

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.

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.