Mozilla Thunderbird is a standalone mail and newsgroup client. Security Fix(es): * firefox: thunderbird: Use-after-free in the JavaScript Engine component (CVE-2026-4701) * firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149 (CVE-2026-4721) * firefox: thunderbird: Privilege escalation in the Netmonitor component (CVE-2026-4717) * firefox: thunderbird: Sandbox escape due to use-after-free in the Disability Access APIs component (CVE-2026-4688) * firefox: thunderbird: Incorrect boundary conditions in the Graphics: Canvas2D component (CVE-2026-4706) * firefox: thunderbird: Incorrect boundary conditions in the Audio/Video: Web Codecs component (CVE-2026-4695) * firefox: thunderbird: Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component (CVE-2026-4689) * firefox: thunderbird: JIT miscompilation in the JavaScript Engine: JIT component (CVE-2026-4698) * firefox: thunderbird: Incorrect boundary conditions, uninitialized memory in the JavaScript Engine component (CVE-2026-4716) * firefox: thunderbird: Race condition, use-after-free in the Graphics: WebRender component (CVE-2026-4684) * firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component (CVE-2026-4705) * firefox: thunderbird: Uninitialized memory in the Graphics: Canvas2D component (CVE-2026-4715) * firefox: thunderbird: Incorrect boundary conditions in the Graphics: Canvas2D component (CVE-2026-4685) * firefox: thunderbird: Incorrect boundary conditions in the Audio/Video component (CVE-2026-4714) * firefox: thunderbird: Incorrect boundary conditions in the Audio/Video: GMP component (CVE-2026-4709) * firefox: thunderbird: Incorrect boundary conditions in the Audio/Video component (CVE-2026-4710) * firefox: thunderbird: Information disclosure in the Widget: Cocoa component (CVE-2026-4712) * firefox: thunderbird: Incorrect boundary conditions in the Audio/Video: Web Codecs component (CVE-2026-4697) * firefox: thunderbird: Incorrect boundary conditions in the Graphics component (CVE-2026-4713) * firefox: thunderbird: Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component (CVE-2026-4690) * firefox: thunderbird: Use-after-free in the Widget: Cocoa component (CVE-2026-4711) * firefox: thunderbird: Incorrect boundary conditions in the Graphics: Canvas2D component (CVE-2026-4686) * firefox: thunderbird: Incorrect boundary conditions in the Graphics component (CVE-2026-4708) * firefox: thunderbird: Use-after-free in the CSS Parsing and Computation component (CVE-2026-4691) * firefox: thunderbird: Incorrect boundary conditions in the Layout: Text and Fonts component (CVE-2026-4699) * firefox: thunderbird: Use-after-free in the Layout: Text and Fonts component (CVE-2026-4696) * firefox: thunderbird: Incorrect boundary conditions in the Audio/Video: Playback component (CVE-2026-4693) * firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component (CVE-2026-4718) * firefox: thunderbird: JIT miscompilation in the JavaScript Engine component (CVE-2026-4702) * firefox: thunderbird: Incorrect boundary conditions in the Graphics: Text component (CVE-2026-4719) * firefox: thunderbird: Incorrect boundary conditions, integer overflow in the Graphics component (CVE-2026-4694) * firefox: thunderbird: Sandbox escape in the Responsive Design Mode component (CVE-2026-4692) * firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149 (CVE-2026-4720) * firefox: thunderbird: Mitigation bypass in the Networking: HTTP component (CVE-2026-4700) * firefox: thunderbird: Incorrect boundary conditions in the Graphics: Canvas2D component (CVE-2026-4707) * firefox: thunderbird: Denial-of-service in the WebRTC: Signaling component (CVE-2026-4704) * firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Telemetry component (CVE-2026-4687) * thunderbird: Out of bounds read in IMAP parsing (CVE-2026-4371) * thunderbird: Spoofing issue in Thunderbird (CVE-2026-3889) 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.