Malicious calendar invitations could use file URI attachments to launch local or network-hosted executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new invitation display enabled, the attachment could also appear under a misleading filename. This vulnerability was fixed in Thunderbird 154 and Thunderbird 153.2.

The AlmaLinux 9.2 host has a package installed that is affected by multiple vulnerabilities as referenced in the TuxCare ALMALINUX9.2:CLSA-2026:1788696027 advisory.

  - Site isolation issue in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154,     Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and     Thunderbird 153.1. (CVE-2026-74934)

  - Privilege escalation in the DOM: Networking component. This vulnerability was fixed in Firefox 154,     Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and     Thunderbird 153.1. (CVE-2026-74935)

  - Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 154,     Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
    (CVE-2026-74936)

  - Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 154, Firefox ESR     153.1, Thunderbird 154, and Thunderbird 153.1. (CVE-2026-74937)

  - Mitigation bypass in the JavaScript: GC component. This vulnerability was fixed in Firefox 154, Firefox     ESR 153.1, Thunderbird 154, and Thunderbird 153.1. (CVE-2026-74938)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - Malicious calendar invitations could use file URI attachments to launch local or network-hosted     executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new     invitation display enabled, the attachment could also appear under a misleading filename. This     vulnerability was fixed in Thunderbird 154 and Thunderbird 153.2. (CVE-2026-84637)

Note that Nessus relies on the presence of the package as reported by the vendor.

The version of Thunderbird installed on the remote macOS or Mac OS X host is prior to 153.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-88 advisory.

  - Privilege escalation due to invalid pointer in the Graphics component. This vulnerability was fixed in     Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird     140.15, and Thunderbird 153.2. (CVE-2026-84131)

  - Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154,     Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and     Thunderbird 153.2. (CVE-2026-75874)

  - Triggering an error condition in certain MIME bodies would cause uninitialized memory to be used.
    (CVE-2026-84639)

  - A maliciously constructed mail header could lead to a one byte read past the end of a buffer.
    (CVE-2026-84640)

  - A malicious IMAP server can trigger use-after-free and heap-memory disclosure by sending a crafted ID     response. Heap contents can ultimately be persisted to prefs.js. (CVE-2026-84641)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of Thunderbird installed on the remote Windows host is prior to 153.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-88 advisory.

  - Privilege escalation due to invalid pointer in the Graphics component. This vulnerability was fixed in     Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird     140.15, and Thunderbird 153.2. (CVE-2026-84131)

  - Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154,     Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and     Thunderbird 153.2. (CVE-2026-75874)

  - Triggering an error condition in certain MIME bodies would cause uninitialized memory to be used.
    (CVE-2026-84639)

  - A maliciously constructed mail header could lead to a one byte read past the end of a buffer.
    (CVE-2026-84640)

  - A malicious IMAP server can trigger use-after-free and heap-memory disclosure by sending a crafted ID     response. Heap contents can ultimately be persisted to prefs.js. (CVE-2026-84641)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of Thunderbird installed on the remote macOS or Mac OS X host is prior to 154.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-78 advisory.

  - Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 154, Firefox ESR     140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1. (CVE-2026-74944)

  - Malicious calendar invitations could use file URI attachments to launch local or network-hosted     executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new     invitation display enabled, the attachment could also appear under a misleading filename. (CVE-2026-84637)

  - Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154,     Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and     Thunderbird 153.2. (CVE-2026-75874)

  - Site isolation issue in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154,     Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and     Thunderbird 153.1. (CVE-2026-74934)

  - Privilege escalation in the DOM: Networking component. This vulnerability was fixed in Firefox 154,     Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and     Thunderbird 153.1. (CVE-2026-74935)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of Thunderbird installed on the remote Windows host is prior to 154.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-78 advisory.

  - Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 154, Firefox ESR     140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1. (CVE-2026-74944)

  - Malicious calendar invitations could use file URI attachments to launch local or network-hosted     executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new     invitation display enabled, the attachment could also appear under a misleading filename. (CVE-2026-84637)

  - Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154,     Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and     Thunderbird 153.2. (CVE-2026-75874)

  - Site isolation issue in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154,     Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and     Thunderbird 153.1. (CVE-2026-74934)

  - Privilege escalation in the DOM: Networking component. This vulnerability was fixed in Firefox 154,     Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and     Thunderbird 153.1. (CVE-2026-74935)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Type	Severity
360485	AlmaLinux 9.2 [TuxCare] Security Update: thunderbird Multiple Vulnerabilities (ALMALINUX9.2:CLSA-2026:1788696027)	Nessus	Alma Linux Local Security Checks	Local	critical
348282	SUSE SLED15: MozillaThunderbird / MozillaThunderbird-translations-common / etc (SUSE-SU-2026:4268-1)	Nessus	SuSE Local Security Checks	Local	critical
342316	Linux Distros Unpatched Vulnerability : CVE-2026-84637	Nessus	Misc.	Local	critical
342260	Mozilla Thunderbird < 153.2	Nessus	MacOS X Local Security Checks	Local	critical
342259	Mozilla Thunderbird < 153.2	Nessus	Windows	Local	critical
337889	Mozilla Thunderbird < 154.0	Nessus	MacOS X Local Security Checks	Local	critical
337888	Mozilla Thunderbird < 154.0	Nessus	Windows	Local	critical

Detections

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CVE-2026-84637

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Tenable Plugins

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