Privilege escalation in the Application Update component. This vulnerability was fixed in Firefox 154 and Thunderbird 154.

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.

  - Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154 and     Thunderbird 154. (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)

  - 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)

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.

  - Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154 and     Thunderbird 154. (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)

  - 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)

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 Firefox installed on the remote Windows host is prior to 154.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-74 advisory.

  - Internally found bugs present in Firefox ESR 115.38, Firefox ESR 140.13, Firefox ESR 153.0 and Firefox     153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we     presume that with enough effort some of these could have been exploited. (CVE-2026-74990)

  - Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs     showed evidence of memory corruption or another security-relevant defect and we presume that with enough     effort some of these could have been exploited. (CVE-2026-74987)

  - Internally found bugs present in Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of     memory corruption or another security-relevant defect and we presume that with enough effort some of these     could have been exploited. (CVE-2026-74988)

  - Internally found bugs present in Firefox 153. Some of these bugs showed evidence of memory corruption or     another security-relevant defect and we presume that with enough effort some of these could have been     exploited. (CVE-2026-74989)

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 Firefox 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 mfsa2026-74 advisory.

  - Internally found bugs present in Firefox ESR 115.38, Firefox ESR 140.13, Firefox ESR 153.0 and Firefox     153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we     presume that with enough effort some of these could have been exploited. (CVE-2026-74990)

  - Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs     showed evidence of memory corruption or another security-relevant defect and we presume that with enough     effort some of these could have been exploited. (CVE-2026-74987)

  - Internally found bugs present in Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of     memory corruption or another security-relevant defect and we presume that with enough effort some of these     could have been exploited. (CVE-2026-74988)

  - Internally found bugs present in Firefox 153. Some of these bugs showed evidence of memory corruption or     another security-relevant defect and we presume that with enough effort some of these could have been     exploited. (CVE-2026-74989)

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
337889	Mozilla Thunderbird < 154.0	Nessus	MacOS X Local Security Checks	Local	critical
337888	Mozilla Thunderbird < 154.0	Nessus	Windows	Local	critical
337629	Mozilla Firefox < 154.0	Nessus	Windows	Local	critical
337625	Mozilla Firefox < 154.0	Nessus	MacOS X Local Security Checks	Local	critical

Detections

Analytics

CVE-2026-74952

high

Tenable Plugins

critical

critical

critical

critical