Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 149.0.2, Firefox ESR < 115.34.1, Firefox ESR < 140.9.1, Thunderbird < 149.0.2, and Thunderbird < 140.9.1.

slackware SSA:2026-098-02: [slackware-security] mozilla-thunderbird (SSA:2026-098-02)

slackware SSA:2026-098-01: [slackware-security] mozilla-firefox (SSA:2026-098-01)

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

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability     affects Firefox < 149.0.2, Firefox ESR < 115.34.1, Firefox ESR < 140.9.1, Thunderbird < 149.0.2, and     Thunderbird < 140.9.1. (CVE-2026-5731)

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

The version of Thunderbird installed on the remote Windows host is prior to 140.9.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-29 advisory.

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

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 149.0.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-28 advisory.

  - Memory safety bugs present in Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence     of memory corruption and we presume that with enough effort some of these could have been exploited to run     arbitrary code. (CVE-2026-5735)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Incorrect boundary conditions in the Graphics: WebGPU component. This vulnerability affects Firefox <     149.0.2. (CVE-2026-5733)

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

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 140.9.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-29 advisory.

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

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 149.0.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-28 advisory.

  - Memory safety bugs present in Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence     of memory corruption and we presume that with enough effort some of these could have been exploited to run     arbitrary code. (CVE-2026-5735)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Incorrect boundary conditions in the Graphics: WebGPU component. This vulnerability affects Firefox <     149.0.2. (CVE-2026-5733)

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

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 149.0.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-25 advisory.

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Incorrect boundary conditions in the Graphics: WebGPU component. This vulnerability affects Firefox <     149.0.2. (CVE-2026-5733)

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

  - Memory safety bugs present in Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence     of memory corruption and we presume that with enough effort some of these could have been exploited to run     arbitrary code. (CVE-2026-5735)

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 ESR installed on the remote macOS or Mac OS X host is prior to 140.9.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-27 advisory.

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

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 ESR installed on the remote macOS or Mac OS X host is prior to 115.34.1. It is, therefore, affected by a vulnerability as referenced in the mfsa2026-26 advisory.

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

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

The version of Firefox ESR installed on the remote Windows host is prior to 140.9.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-27 advisory.

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

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 ESR installed on the remote Windows host is prior to 115.34.1. It is, therefore, affected by a vulnerability as referenced in the mfsa2026-26 advisory.

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

Note that Nessus has not tested for this issue 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 149.0.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-25 advisory.

  - Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox     149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume     that with enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5731)

  - Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability     affects Firefox < 149.0.2 and Firefox ESR < 140.9.1. (CVE-2026-5732)

  - Incorrect boundary conditions in the Graphics: WebGPU component. This vulnerability affects Firefox <     149.0.2. (CVE-2026-5733)

  - Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and     Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with     enough effort some of these could have been exploited to run arbitrary code. (CVE-2026-5734)

  - Memory safety bugs present in Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence     of memory corruption and we presume that with enough effort some of these could have been exploited to run     arbitrary code. (CVE-2026-5735)

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	Severity
305253	Linux Distros Unpatched Vulnerability : CVE-2026-5731	Nessus	Misc.	critical
305199	Mozilla Thunderbird < 140.9.1	Nessus	Windows	critical
305198	Mozilla Thunderbird < 149.0.2	Nessus	MacOS X Local Security Checks	critical
305197	Mozilla Thunderbird < 140.9.1	Nessus	MacOS X Local Security Checks	critical
305196	Mozilla Thunderbird < 149.0.2	Nessus	Windows	critical
305162	Mozilla Firefox < 149.0.2	Nessus	Windows	critical
305161	Mozilla Firefox ESR < 140.9.1	Nessus	MacOS X Local Security Checks	critical
305160	Mozilla Firefox ESR < 115.34.1	Nessus	MacOS X Local Security Checks	critical
305159	Mozilla Firefox ESR < 140.9.1	Nessus	Windows	critical
305158	Mozilla Firefox ESR < 115.34.1	Nessus	Windows	critical
305157	Mozilla Firefox < 149.0.2	Nessus	MacOS X Local Security Checks	critical

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