There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - Mozilla developers and community members reported memory safety bugs present in Firefox 87. 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 < 88. (CVE-2021-29947)

  - A WebGL framebuffer was not initialized early enough, resulting in memory corruption and an out of bound
    write. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.
    (CVE-2021-23994)

  - When Responsive Design Mode was enabled, it used references to objects that were previously freed. We
    presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability
    affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88. (CVE-2021-23995)

  - By utilizing 3D CSS in conjunction with Javascript, content could have been rendered outside the webpage's
    viewport, resulting in a spoofing attack that could have been used for phishing or other attacks on a
    user. This vulnerability affects Firefox < 88. (CVE-2021-23996)

  - Due to unexpected data type conversions, a use-after-free could have occurred when interacting with the
    font cache. We presume that with enough effort this could have been exploited to run arbitrary code. This
    vulnerability affects Firefox < 88. (CVE-2021-23997)

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-4926-1 advisory.

    Multiple security issues were discovered in Firefox. If a user were tricked into opening a specially     crafted website, an attacker could potentially exploit these to cause a denial of service, spoof the     browser UI, bypass security restrictions, trick the user into disclosing confidential information, or     execute arbitrary code. (CVE-2021-23994, CVE-2021-23996, CVE-2021-23997, CVE-2021-23998, CVE-2021-23999,     CVE-2021-24000, CVE-2021-24001, CVE-2021-29945, CVE-2021-29946, CVE-2021-29947)

    A use-after-free was discovered when Responsive Design Mode was enabled. If a user were tricked into     opening a specially crafted website with Responsive Design Mode enabled, an attacker could potentially     exploit this to cause a denial of service, or execute arbitrary code. (CVE-2021-23995)

    It was discovered that Firefox mishandled ftp URLs with encoded newline characters. If a user were tricked     into clicking on a specially crafted link, an attacker could potentially exploit this to send arbitrary     FTP commands. (CVE-2021-24002)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

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 88.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2021-16 advisory.

  - Mozilla developers and community members Ryan VanderMeulen, Sean Feng, Tyson Smith, Julian Seward,     Christian Holler reported memory safety bugs present in Firefox 87. 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-2021-29947)

  - A WebGL framebuffer was not initialized early enough, resulting in memory corruption and an out of bound     write. (CVE-2021-23994)

  - When Responsive Design Mode was enabled, it used references to objects that were previously freed. We     presume that with enough effort this could have been exploited to run arbitrary code. (CVE-2021-23995)

  - By utilizing 3D CSS in conjunction with Javascript, content could have been rendered outside the webpage's     viewport, resulting in a spoofing attack that could have been used for phishing or other attacks on a     user. (CVE-2021-23996)

  - Due to unexpected data type conversions, a use-after-free could have occurred when interacting with the     font cache. We presume that with enough effort this could have been exploited to run arbitrary code.
    (CVE-2021-23997)

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 88.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2021-16 advisory.

  - Mozilla developers and community members Ryan VanderMeulen, Sean Feng, Tyson Smith, Julian Seward,     Christian Holler reported memory safety bugs present in Firefox 87. 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-2021-29947)

  - A WebGL framebuffer was not initialized early enough, resulting in memory corruption and an out of bound     write. (CVE-2021-23994)

  - When Responsive Design Mode was enabled, it used references to objects that were previously freed. We     presume that with enough effort this could have been exploited to run arbitrary code. (CVE-2021-23995)

  - By utilizing 3D CSS in conjunction with Javascript, content could have been rendered outside the webpage's     viewport, resulting in a spoofing attack that could have been used for phishing or other attacks on a     user. (CVE-2021-23996)

  - Due to unexpected data type conversions, a use-after-free could have occurred when interacting with the     font cache. We presume that with enough effort this could have been exploited to run arbitrary code.
    (CVE-2021-23997)

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.

  - By utilizing 3D CSS in conjunction with Javascript, content could have been rendered outside the webpage's     viewport, resulting in a spoofing attack that could have been used for phishing or other attacks on a     user. This vulnerability affects Firefox < 88. (CVE-2021-23996)

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

ID	Name	Product	Family	Published	Updated	Severity
427627	Alpine: multiple librewolf packages: security update to 88.0-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	5/16/2025	7/2/2026	high
427627	Alpine: multiple librewolf packages: security update to 88.0-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	5/16/2025	7/2/2026	high
404380	Alpine: multiple firefox packages: security update to 88.0-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
404380	Alpine: multiple firefox packages: security update to 88.0-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
148992	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Firefox vulnerabilities (USN-4926-1)	Nessus	Ubuntu Local Security Checks	4/26/2021	8/28/2024	high
148766	Mozilla Firefox < 88.0	Nessus	MacOS X Local Security Checks	4/19/2021	11/18/2025	high
148767	Mozilla Firefox < 88.0	Nessus	Windows	4/19/2021	11/18/2025	high
244601	Linux Distros Unpatched Vulnerability : CVE-2021-23996	Nessus	Misc.	8/7/2025	7/28/2026	medium

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