RHSA-2026:80503 — Security Advisory

An update for thunderbird is now available for Red Hat Enterprise Linux 9.6 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.

Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

• firefox: thunderbird: Privilege escalation in the DOM: Workers component (CVE-2026-16365)

• firefox: thunderbird: Sandbox escape in the Remote Settings Client component (CVE-2026-75874)

• firefox: Sandbox escape due to use-after-free in the DOM: Security component (CVE-2026-84121)

• firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2, Firefox ESR 140.15 and Firefox ESR 115.40 (CVE-2026-84145)

• firefox: Sandbox escape due to use-after-free in the DOM: Navigation component (CVE-2026-84119)

• firefox: Use-after-free in the Audio/Video component (CVE-2026-84120)

• firefox: Privilege escalation due to invalid pointer in the Graphics component (CVE-2026-84131)

• firefox: Use-after-free in the DOM: Core & HTML component (CVE-2026-84124)

• firefox: Use-after-free in the Audio/Video component (CVE-2026-84122)

• firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15 (CVE-2026-84143)

• thunderbird: Uninitialized memory in MIME parsing (CVE-2026-84639)

• thunderbird: Information disclosure due to malicious IMAP server response (CVE-2026-84641)

• thunderbird: One byte overflow read in mail parser (CVE-2026-84640)

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.