RHSA-2026:85244 - Security Advisory

Topic

An update for thunderbird is now available for Red Hat Enterprise Linux 9.6 Extended Update 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 Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

• firefox: thunderbird: Use-after-free in the Graphics: Canvas2D component (CVE-2026-100832)
• firefox: Use-after-free in the Layout: Text and Fonts component (CVE-2026-100784)
• firefox: thunderbird: Privilege escalation in the DLL Services component (CVE-2026-100801)
• firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Internationalization component (CVE-2026-100794)
• firefox: thunderbird: Privilege escalation in the Address Bar component (CVE-2026-100820)
• firefox: thunderbird: Use-after-free in the Graphics: Canvas2D component (CVE-2026-100777)
• firefox: thunderbird: Information disclosure in the Networking: JAR component (CVE-2026-100766)
• firefox: thunderbird: Use-after-free in the XSLT component (CVE-2026-100779)
• firefox: thunderbird: Privilege escalation in the DOM: Service Workers component (CVE-2026-100807)
• firefox: thunderbird: JIT miscompilation in the JavaScript: WebAssembly component (CVE-2026-100792)
• firefox: Privilege escalation due to use-after-free in the Graphics: WebRender component (CVE-2026-100797)
• firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the XPCOM component (CVE-2026-100819)
• firefox: thunderbird: Use-after-free in the JavaScript: WebAssembly component (CVE-2026-100776)
• firefox: thunderbird: Use-after-free in the Widget component (CVE-2026-100757)
• firefox: Sandbox escape due to use-after-free in the Graphics component (CVE-2026-100786)
• firefox: thunderbird: Information disclosure in the Networking component (CVE-2026-96869)
• firefox: Sandbox escape due to use-after-free in the DOM: Content Processes component (CVE-2026-100770)
• firefox: thunderbird: Use-after-free in the JavaScript: WebAssembly component (CVE-2026-100769)
• firefox: Use-after-free in the DOM: Core & HTML component (CVE-2026-100791)
• firefox: thunderbird: Sandbox escape due to use-after-free in the Widget: Gtk component (CVE-2026-100818)
• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics component (CVE-2026-100782)
• firefox: firefox: Sandbox escape via use-after-free in DOM component (CVE-2026-100811)
• firefox: thunderbird: Use-after-free in the DOM: Core & HTML component (CVE-2026-100772)
• firefox: thunderbird: Uninitialized memory in the Storage: Quota Manager component (CVE-2026-100759)
• firefox: Sandbox escape due to use-after-free in the DOM: Core & HTML component (CVE-2026-100778)
• firefox: thunderbird: Sandbox escape in the DOM: Navigation component (CVE-2026-100758)
• firefox: thunderbird: Sandbox escape in the Graphics component (CVE-2026-100775)
• firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component (CVE-2026-100781)
• firefox: Use-after-free in the DOM: Core & HTML component (CVE-2026-100774)
• firefox: thunderbird: Same-origin policy bypass in the WebExtensions component (CVE-2026-100803)
• firefox: thunderbird: Use-after-free in the Graphics: Canvas2D component (CVE-2026-100789)
• firefox: thunderbird: Use-after-free in the DOM: Core & HTML component (CVE-2026-100785)
• firefox: thunderbird: Site isolation issue in the Panning and Zooming component (CVE-2026-100821)
• firefox: thunderbird: Invalid pointer in the JavaScript: WebAssembly component (CVE-2026-100788)
• firefox: thunderbird: Undefined behavior in the DOM: Streams component (CVE-2026-100771)
• firefox: Sandbox escape due to use-after-free in the DOM: Content Processes component (CVE-2026-100762)
• firefox: thunderbird: Use-after-free in the XSLT component (CVE-2026-100790)
• firefox: thunderbird: Use-after-free in the Storage: IndexedDB component (CVE-2026-100773)
• firefox: thunderbird: Use-after-free in the DOM: Core & HTML component (CVE-2026-100780)
• firefox: thunderbird: Use-after-free in the Networking: Cache component (CVE-2026-100767)
• firefox: thunderbird: Incorrect boundary conditions in the Audio/Video: Playback component (CVE-2026-100756)
• firefox: thunderbird: Uninitialized memory in the Audio/Video component (CVE-2026-100783)

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 9.6 x86_64
• Red Hat Enterprise Linux Server - AUS 9.6 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 9.6 s390x
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 9.6 ppc64le
• Red Hat Enterprise Linux for ARM 64 - Extended Update Support 9.6 aarch64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 9.6 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 9.6 x86_64
• Red Hat Enterprise Linux for ARM 64 - 4 years of updates 9.6 aarch64
• Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 9.6 s390x
• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 9.6 x86_64
• Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 9.6 aarch64
• Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 9.6 ppc64le
• Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 9.6 s390x

Fixes

• BZ - 2543113 - CVE-2026-100832 firefox: thunderbird: Use-after-free in the Graphics: Canvas2D component
• BZ - 2543114 - CVE-2026-100784 firefox: Use-after-free in the Layout: Text and Fonts component
• BZ - 2543116 - CVE-2026-100801 firefox: thunderbird: Privilege escalation in the DLL Services component
• BZ - 2543120 - CVE-2026-100794 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Internationalization component
• BZ - 2543123 - CVE-2026-100777 firefox: thunderbird: Use-after-free in the Graphics: Canvas2D component
• BZ - 2543125 - CVE-2026-100766 firefox: thunderbird: Information disclosure in the Networking: JAR component
• BZ - 2543128 - CVE-2026-100779 firefox: thunderbird: Use-after-free in the XSLT component
• BZ - 2543130 - CVE-2026-100807 firefox: thunderbird: Privilege escalation in the DOM: Service Workers component
• BZ - 2543131 - CVE-2026-100792 firefox: thunderbird: JIT miscompilation in the JavaScript: WebAssembly component
• BZ - 2543133 - CVE-2026-100797 firefox: Privilege escalation due to use-after-free in the Graphics: WebRender component
• BZ - 2543134 - CVE-2026-100819 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the XPCOM component
• BZ - 2543137 - CVE-2026-100776 firefox: thunderbird: Use-after-free in the JavaScript: WebAssembly component
• BZ - 2543140 - CVE-2026-100757 firefox: thunderbird: Use-after-free in the Widget component
• BZ - 2543142 - CVE-2026-100786 firefox: Sandbox escape due to use-after-free in the Graphics component
• BZ - 2543145 - CVE-2026-100770 firefox: Sandbox escape due to use-after-free in the DOM: Content Processes component
• BZ - 2543146 - CVE-2026-100769 firefox: thunderbird: Use-after-free in the JavaScript: WebAssembly component
• BZ - 2543149 - CVE-2026-100791 firefox: Use-after-free in the DOM: Core & HTML component
• BZ - 2543150 - CVE-2026-100818 firefox: thunderbird: Sandbox escape due to use-after-free in the Widget: Gtk component
• BZ - 2543152 - CVE-2026-100782 firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics component
• BZ - 2543154 - CVE-2026-100811 firefox: firefox: Sandbox escape via use-after-free in DOM component
• BZ - 2543155 - CVE-2026-100772 firefox: thunderbird: Use-after-free in the DOM: Core & HTML component
• BZ - 2543156 - CVE-2026-100759 firefox: thunderbird: Uninitialized memory in the Storage: Quota Manager component
• BZ - 2543157 - CVE-2026-100778 firefox: Sandbox escape due to use-after-free in the DOM: Core & HTML component
• BZ - 2543159 - CVE-2026-100758 firefox: thunderbird: Sandbox escape in the DOM: Navigation component
• BZ - 2543160 - CVE-2026-100775 firefox: thunderbird: Sandbox escape in the Graphics component
• BZ - 2543161 - CVE-2026-100781 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component
• BZ - 2543163 - CVE-2026-100774 firefox: Use-after-free in the DOM: Core & HTML component
• BZ - 2543164 - CVE-2026-100803 firefox: thunderbird: Same-origin policy bypass in the WebExtensions component
• BZ - 2543166 - CVE-2026-100789 firefox: thunderbird: Use-after-free in the Graphics: Canvas2D component
• BZ - 2543167 - CVE-2026-100785 firefox: thunderbird: Use-after-free in the DOM: Core & HTML component
• BZ - 2543172 - CVE-2026-100821 firefox: thunderbird: Site isolation issue in the Panning and Zooming component
• BZ - 2543174 - CVE-2026-100788 firefox: thunderbird: Invalid pointer in the JavaScript: WebAssembly component
• BZ - 2543177 - CVE-2026-100771 firefox: thunderbird: Undefined behavior in the DOM: Streams component
• BZ - 2543182 - CVE-2026-100762 firefox: Sandbox escape due to use-after-free in the DOM: Content Processes component
• BZ - 2543183 - CVE-2026-100790 firefox: thunderbird: Use-after-free in the XSLT component
• BZ - 2543185 - CVE-2026-100773 firefox: thunderbird: Use-after-free in the Storage: IndexedDB component
• BZ - 2543187 - CVE-2026-100780 firefox: thunderbird: Use-after-free in the DOM: Core & HTML component
• BZ - 2543188 - CVE-2026-100767 firefox: thunderbird: Use-after-free in the Networking: Cache component
• BZ - 2543192 - CVE-2026-100756 firefox: thunderbird: Incorrect boundary conditions in the Audio/Video: Playback component
• BZ - 2543193 - CVE-2026-100783 firefox: thunderbird: Uninitialized memory in the Audio/Video component

CVEs

• CVE-2026-96869
• CVE-2026-100756
• CVE-2026-100757
• CVE-2026-100758
• CVE-2026-100759
• CVE-2026-100762
• CVE-2026-100766
• CVE-2026-100767
• CVE-2026-100769
• CVE-2026-100770
• CVE-2026-100771
• CVE-2026-100772
• CVE-2026-100773
• CVE-2026-100774
• CVE-2026-100775
• CVE-2026-100776
• CVE-2026-100777
• CVE-2026-100778
• CVE-2026-100779
• CVE-2026-100780
• CVE-2026-100781
• CVE-2026-100782
• CVE-2026-100783
• CVE-2026-100784
• CVE-2026-100785
• CVE-2026-100786
• CVE-2026-100788
• CVE-2026-100789
• CVE-2026-100790
• CVE-2026-100791
• CVE-2026-100792
• CVE-2026-100794
• CVE-2026-100797
• CVE-2026-100801
• CVE-2026-100803
• CVE-2026-100807
• CVE-2026-100811
• CVE-2026-100818
• CVE-2026-100819
• CVE-2026-100820
• CVE-2026-100821
• CVE-2026-100832

References

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