RHSA-2026:13977 - Security Advisory

Topic

An update for firefox is now available for Red Hat Enterprise Linux 7 Extended Lifecycle 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.

Description

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

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 Server - Extended Life Cycle Support 7 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 7 s390x
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, big endian 7 ppc64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, little endian 7 ppc64le

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
• RHEL-147877 - Firefox 140 ESR does not recognize CA certificates added to the system trust store

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