This Red Hat Security Advisory addresses multiple critical vulnerabilities in Firefox, including memory safety bugs (CVE-2026-5734, CVSS 9.8) and libpng flaws like a use-after-free (CVE-2026-33416, CVSS 7.5) that can lead to arbitrary code execution or information disclosure. Affected versions include Firefox prior to 140.9.1 and 149.0.2, and libpng versions from 1.2.1 to before 1.6.56. The update provides the patched Firefox packages for Red Hat Enterprise Linux 8.4 support streams, requiring immediate application.
Red Hat Product Errata RHSA-2026:13600 - Security Advisory Issued: 2026-05-05 Updated: 2026-05-05 RHSA-2026:13600 - Security Advisory Overview Updated Packages Synopsis Important: firefox security update Type/Severity Security Advisory: Important Red Hat Lightspeed patch analysis Identify and remediate systems affected by this advisory. View affected systems 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): 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 8.4 x86_64 Red Hat Enterprise Linux Server - AUS 8.4 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 Note: More recent versions of these packages may be available. Click a package name for more details. Red Hat Enterprise Linux for x86_64 - Extended Update Support Extension 8.4 SRPM firefox-140.9.1-1.el8_4.src.rpm SHA-256: 4d83a2a7c2635104c34aa18ca6ede2720eb54c65ab11d21b86198129366ef5b1 x86_64 firefox-140.9.1-1.el8_4.x86_64.rpm SHA-256: 341f6154dac23e1b5a6f2f97130d5fdff75da4870ea6f816771338f278077684 firefox-debuginfo-140.9.1-1.el8_4.x86_64.rpm SHA-256: c950c3bd4cb53dba68cda67b673e1c930abe65618991c0f75b263f793d181195 firefox-debugsource-140.9.1-1.el8_4.x86_64.rpm SHA-256: e990b8af772a99b6ebe7d1c5487003e8e2468aaa9a1c6578de7b48b49d4f4487 Red Hat Enterprise Linux Server - AUS 8.4 SRPM firefox-140.9.1-1.el8_4.src.rpm SHA-256: 4d83a2a7c2635104c34aa18ca6ede2720eb54c65ab11d21b86198129366ef5b1 x86_64 firefox-140.9.1-1.el8_4.x86_64.rpm SHA-256: 341f6154dac23e1b5a6f2f97130d5fdff75da4870ea6f816771338f278077684 firefox-debuginfo-140.9.1-1.el8_4.x86_64.rpm SHA-256: c950c3bd4cb53dba68cda67b673e1c930abe65618991c0f75b263f793d181195 firefox-debugsource-140.9.1-1.el8_4.x86_64.rpm SHA-256: e990b8af772a99b6ebe7d1c5487003e8e2468aaa9a1c6578de7b48b49d4f4487 The Red Hat security contact is secalert@redhat.com . More contact details at https://access.redhat.com/security/team/contact/ .