RHSA-2026:15889 - 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):

• libpng: libpng: Arbitrary code execution due to use-after-free vulnerability (CVE-2026-33416)
• libpng: libpng: Information disclosure and denial of service via out-of-bounds read/write in Neon palette expansion (CVE-2026-33636)
• thunderbird: firefox: Memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2 (CVE-2026-5734)
• thunderbird: firefox: Memory safety bugs fixed in Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2 (CVE-2026-5731)
• firefox: thunderbird: Incorrect boundary conditions, integer overflow in the Graphics: Text component (CVE-2026-5732)

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 - 2451805 - CVE-2026-33416 libpng: libpng: Arbitrary code execution due to use-after-free vulnerability
• BZ - 2451819 - CVE-2026-33636 libpng: libpng: Information disclosure and denial of service via out-of-bounds read/write in Neon palette expansion
• BZ - 2455897 - CVE-2026-5734 thunderbird: firefox: Memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2
• BZ - 2455901 - CVE-2026-5731 thunderbird: firefox: Memory safety bugs fixed in Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2
• BZ - 2455908 - CVE-2026-5732 firefox: thunderbird: Incorrect boundary conditions, integer overflow in the Graphics: Text component

CVEs

• CVE-2026-5731
• CVE-2026-5732
• CVE-2026-5734
• CVE-2026-33416
• CVE-2026-33636

References

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