RHSA-2026:81913 — Security Advisory

An update for thunderbird is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.6 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.

Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

• firefox: thunderbird: Privilege escalation in the DOM: Workers component (CVE-2026-16365)

• firefox: thunderbird: Sandbox escape in the Remote Settings Client component (CVE-2026-75874)

• firefox: Sandbox escape due to use-after-free in the DOM: Security component (CVE-2026-84121)

• firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2, Firefox ESR 140.15 and Firefox ESR 115.40 (CVE-2026-84145)

• firefox: Sandbox escape due to use-after-free in the DOM: Navigation component (CVE-2026-84119)

• firefox: Use-after-free in the Audio/Video component (CVE-2026-84120)

• firefox: Privilege escalation due to invalid pointer in the Graphics component (CVE-2026-84131)

• firefox: Use-after-free in the DOM: Core & HTML component (CVE-2026-84124)

• firefox: Use-after-free in the Audio/Video component (CVE-2026-84122)

• firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15 (CVE-2026-84143)

• thunderbird: Uninitialized memory in MIME parsing (CVE-2026-84639)

• thunderbird: Information disclosure due to malicious IMAP server response (CVE-2026-84641)

• thunderbird: One byte overflow read in mail parser (CVE-2026-84640)

• firefox: thunderbird: Use-after-free in the SVG component (CVE-2026-92024)

• firefox: thunderbird: Mitigation bypass in the Remote Settings Client component (CVE-2026-92019)

• firefox: thunderbird: Use-after-free in the Networking component (CVE-2026-92026)

• firefox: thunderbird: Information disclosure in the Graphics: ImageLib component (CVE-2026-92031)

• firefox: thunderbird: Sandbox escape due to invalid pointer in the Graphics component (CVE-2026-92032)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92010)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92006)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92011)

• firefox: thunderbird: Use-after-free in the DOM: Streams component (CVE-2026-92027)

• firefox: thunderbird: Use-after-free in the DOM: Core & HTML component (CVE-2026-92028)

• firefox: thunderbird: Privilege escalation in the WebExtensions component (CVE-2026-92015)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92013)

• firefox: thunderbird: Use-after-free in the Disability Access APIs component (CVE-2026-92016)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92012)

• firefox: thunderbird: Use-after-free in the DOM: HTML Parser component (CVE-2026-92022)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics component (CVE-2026-92014)

• firefox: thunderbird: Sandbox escape in the DOM: Core & HTML component (CVE-2026-92018)

• firefox: thunderbird: Use-after-free in the JavaScript Engine: JIT component (CVE-2026-92021)

• firefox: thunderbird: Use-after-free in the Audio/Video: Web Codecs component (CVE-2026-92005)

• firefox: thunderbird: Privilege escalation in the DOM: Service Workers component (CVE-2026-92017)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92009)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: WebRender component (CVE-2026-92020)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92008)

• firefox: thunderbird: Mitigation bypass in the DOM: Copy & Paste and Drag & Drop component (CVE-2026-92030)

• firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92007)

• firefox: thunderbird: Use-after-free in the DOM: Navigation component (CVE-2026-92025)

• firefox: thunderbird: Use-after-free in the SVG component (CVE-2026-92029)

• firefox: thunderbird: Use-after-free in the XML component (CVE-2026-92023)

• thunderbird: Out-of-bounds read in IMAP response parser (CVE-2026-92240)

• thunderbird: Thunderbird: Out-of-bounds read via maliciously constructed IMAP line (CVE-2026-92239)

• thunderbird: Thunderbird: Memory safety violations via maliciously crafted mail headers (CVE-2026-92238)

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.