RHSA-2026:76894 - Security Advisory

Topic

An update for firefox is now available for Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On.

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 Firefox is an open-source web browser, designed for standards compliance, performance, and portability.

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)

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 Life Cycle Long Life 8.4 x86_64
• Red Hat Enterprise Linux Server - AUS 8.4 x86_64
• Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle Long Life 8.4 aarch64
• Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle Long Life 8.4 ppc64le
• Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle Long Life 8.4 s390x

Fixes

• BZ - 2503504 - CVE-2026-16365 firefox: thunderbird: Privilege escalation in the DOM: Workers component
• BZ - 2517832 - CVE-2026-75874 firefox: thunderbird: Sandbox escape in the Remote Settings Client component
• BZ - 2526753 - CVE-2026-84121 firefox: Sandbox escape due to use-after-free in the DOM: Security component
• BZ - 2526760 - CVE-2026-84145 firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2, Firefox ESR 140.15 and Firefox ESR 115.40
• BZ - 2526764 - CVE-2026-84119 firefox: Sandbox escape due to use-after-free in the DOM: Navigation component
• BZ - 2526765 - CVE-2026-84120 firefox: Use-after-free in the Audio/Video component
• BZ - 2526767 - CVE-2026-84131 firefox: Privilege escalation due to invalid pointer in the Graphics component
• BZ - 2526773 - CVE-2026-84124 firefox: Use-after-free in the DOM: Core & HTML component
• BZ - 2526778 - CVE-2026-84122 firefox: Use-after-free in the Audio/Video component
• BZ - 2526781 - CVE-2026-84143 firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15

CVEs

• CVE-2026-16365
• CVE-2026-75874
• CVE-2026-84119
• CVE-2026-84120
• CVE-2026-84121
• CVE-2026-84122
• CVE-2026-84124
• CVE-2026-84131
• CVE-2026-84143
• CVE-2026-84145

References

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