ESB-2026.4074
PUBLISHED
CVSS 8.800000190734863 HIGH
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AUSCERT External Security Bulletin Redistribution
ESB-2026.4074
thunderbird security update
23 April 2026
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AUSCERT Security Bulletin Summary
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Product: thunderbird
Publisher: Red Hat
Operating System: Red Hat
Resolution: Patch/Upgrade
CVE Names: CVE-2026-33416 CVE-2026-33636 CVE-2026-5732
CVE-2026-5731 CVE-2026-5734
Original Bulletin:
https://access.redhat.com/errata/RHSA-2026:9638
Comment: CVSS (Max): 8.8 CVE-2026-5734 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H)
CVSS Source: Red Hat
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS (Max): 0.1% (20th) CVE-2026-5731 2026-04-21
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RHSA-2026:9638 - Security Advisory
Issued: 2026-04-22
Updated: 2026-04-22
Synopsis
Thunderbird security update
Type/Severity
Security Advisory: Important
Topic
An update for thunderbird is now available for Red Hat Enterprise Linux 10.
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):
o libpng: libpng: Arbitrary code execution due to use-after-free
vulnerability (CVE-2026-33416)
o libpng: libpng: Information disclosure and denial of service via
out-of-bounds read/write in Neon palette expansion (CVE-2026-33636)
o 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)
o 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)
o 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
o Red Hat Enterprise Linux for x86_64 10 x86_64
o Red Hat Enterprise Linux for IBM z Systems 10 s390x
o Red Hat Enterprise Linux for Power, little endian 10 ppc64le
o Red Hat Enterprise Linux for ARM 64 10 aarch64
Fixes
o BZ - 2451805 - CVE-2026-33416 libpng: libpng: Arbitrary code execution due
to use-after-free vulnerability
o BZ - 2451819 - CVE-2026-33636 libpng: libpng: Information disclosure and
denial of service via out-of-bounds read/write in Neon palette expansion
o 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
o 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
o BZ - 2455908 - CVE-2026-5732 firefox: thunderbird: Incorrect boundary
conditions, integer overflow in the Graphics: Text component
CVEs
o CVE-2026-5731
o CVE-2026-5732
o CVE-2026-5734
o CVE-2026-33416
o CVE-2026-33636
References
o https://access.redhat.com/security/updates/classification/#important
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