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

  - Mozilla developers reported memory safety bugs present in Firefox 91. 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 < 92. (CVE-2021-38494)

  - Uninitialized memory in a canvas object could have caused an incorrect free() leading to memory corruption
    and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91,
    Firefox ESR < 78.13, and Firefox < 91. (CVE-2021-29980)

  - An issue present in lowering/register allocation could have led to obscure but deterministic register
    confusion failures in JITted code that would lead to a potentially exploitable crash. This vulnerability
    affects Firefox < 91 and Thunderbird < 91. (CVE-2021-29981)

  - Due to incorrect JIT optimization, we incorrectly interpreted data from the wrong type of object,
    resulting in the potential leak of a single bit of memory. This vulnerability affects Firefox < 91 and
    Thunderbird < 91. (CVE-2021-29982)

  - Firefox for Android could get stuck in fullscreen mode and not exit it even after normal interactions that
    should cause it to exit. *Note: This issue only affected Firefox for Android. Other operating systems are
    unaffected.*. This vulnerability affects Firefox < 91. (CVE-2021-29983)

The remote Ubuntu 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-5074-1 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, bypass mixed     content blocking, or execute arbitrary code.

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 remote host is affected by the vulnerability described in GLSA-202202-03 (Mozilla Firefox: Multiple vulnerabilities)

  - A malicious webpage could have triggered a use-after-free, memory corruption, and a potentially     exploitable crash. *This bug could only be triggered when accessibility was enabled.*. This vulnerability     affects Thunderbird < 78.12, Firefox ESR < 78.12, and Firefox < 90. (CVE-2021-29970)

  - A use-after-free vulnerability was found via testing, and traced to an out-of-date Cairo library. Updating     the library resolved the issue, and may have remediated other, unknown security vulnerabilities as well.
    This vulnerability affects Firefox < 90. (CVE-2021-29972)

  - When network partitioning was enabled, e.g. as a result of Enhanced Tracking Protection settings, a TLS     error page would allow the user to override an error on a domain which had specified HTTP Strict Transport     Security (which implies that the error should not be override-able.) This issue did not affect the network     connections, and they were correctly upgraded to HTTPS automatically. This vulnerability affects Firefox <     90. (CVE-2021-29974)

  - Through a series of DOM manipulations, a message, over which the attacker had control of the text but not     HTML or formatting, could be overlaid on top of another domain (with the new domain correctly shown in the     address bar) resulting in possible user confusion. This vulnerability affects Firefox < 90.
    (CVE-2021-29975)

  - Mozilla developers reported memory safety bugs present in code shared between Firefox and Thunderbird.
    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 Thunderbird < 78.12,     Firefox ESR < 78.12, and Firefox < 90. (CVE-2021-29976)

  - Mozilla developers reported memory safety bugs present in Firefox 89. 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 < 90. (CVE-2021-29977)

  - Uninitialized memory in a canvas object could have caused an incorrect free() leading to memory corruption     and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91,     Firefox ESR < 78.13, and Firefox < 91. (CVE-2021-29980)

  - An issue present in lowering/register allocation could have led to obscure but deterministic register     confusion failures in JITted code that would lead to a potentially exploitable crash. This vulnerability     affects Firefox < 91 and Thunderbird < 91. (CVE-2021-29981)

  - Due to incorrect JIT optimization, we incorrectly interpreted data from the wrong type of object,     resulting in the potential leak of a single bit of memory. This vulnerability affects Firefox < 91 and     Thunderbird < 91. (CVE-2021-29982)

  - Instruction reordering resulted in a sequence of instructions that would cause an object to be incorrectly     considered during garbage collection. This led to memory corruption and a potentially exploitable crash.
    This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.
    (CVE-2021-29984)

  - A use-after-free vulnerability in media channels could have led to memory corruption and a potentially     exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13,     and Firefox < 91. (CVE-2021-29985)

  - A suspected race condition when calling getaddrinfo led to memory corruption and a potentially exploitable     crash. *Note: This issue only affected Linux operating systems. Other operating systems are unaffected.*     This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.
    (CVE-2021-29986)

  - After requesting multiple permissions, and closing the first permission panel, subsequent permission     panels will be displayed in a different position but still record a click in the default location, making     it possible to trick a user into accepting a permission they did not want to. *This bug only affects     Firefox on Linux. Other operating systems are unaffected.*. This vulnerability affects Firefox < 91 and     Thunderbird < 91. (CVE-2021-29987)

  - Firefox incorrectly treated an inline list-item element as a block element, resulting in an out of bounds     read or memory corruption, and a potentially exploitable crash. This vulnerability affects Thunderbird <     78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91. (CVE-2021-29988)

  - Mozilla developers reported memory safety bugs present in Firefox 90 and Firefox ESR 78.12. 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 Thunderbird < 78.13, Firefox ESR < 78.13,     and Firefox < 91. (CVE-2021-29989)

  - Mozilla developers and community members reported memory safety bugs present in Firefox 90. 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 < 91. (CVE-2021-29990)

  - Out of bounds write in ANGLE in Google Chrome prior to 91.0.4472.101 allowed a remote attacker to     potentially perform out of bounds memory access via a crafted HTML page. (CVE-2021-30547)

  - Mixed-content checks were unable to analyze opaque origins which led to some mixed content being loaded.
    This vulnerability affects Firefox < 92. (CVE-2021-38491)

  - Mozilla developers reported memory safety bugs present in Firefox 91 and Firefox ESR 78.13. 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 ESR < 78.14, Thunderbird < 78.14,     and Firefox < 92. (CVE-2021-38493)

  - Mozilla developers reported memory safety bugs present in Thunderbird 78.13.0. 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 Thunderbird < 91.1 and Firefox ESR < 91.1.
    (CVE-2021-38495)

  - The iframe sandbox rules were not correctly applied to XSLT stylesheets, allowing an iframe to bypass     restrictions such as executing scripts or navigating the top-level frame. This vulnerability affects     Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-38503)

  - When interacting with an HTML input element's file picker dialog with webkitdirectory set, a use-after-     free could have resulted, leading to memory corruption and a potentially exploitable crash. This     vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-38504)

  - Through a series of navigations, Firefox could have entered fullscreen mode without notification or     warning to the user. This could lead to spoofing attacks on the browser UI including phishing. This     vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-38506)

  - The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to be transparently upgraded     to TLS while retaining the visual properties of an HTTP connection, including being same-origin with     unencrypted connections on port 80. However, if a second encrypted port on the same IP address (e.g. port     8443) did not opt-in to opportunistic encryption; a network attacker could forward a connection from the     browser to port 443 to port 8443, causing the browser to treat the content of port 8443 as same-origin     with HTTP. This was resolved by disabling the Opportunistic Encryption feature, which had low usage. This     vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-38507)

  - By displaying a form validity message in the correct location at the same time as a permission prompt     (such as for geolocation), the validity message could have obscured the prompt, resulting in the user     potentially being tricked into granting the permission. This vulnerability affects Firefox < 94,     Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-38508)

  - Due to an unusual sequence of attacker-controlled events, a Javascript alert() dialog with arbitrary     (although unstyled) contents could be displayed over top an uncontrolled webpage of the attacker's     choosing. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.
    (CVE-2021-38509)

  - Under certain circumstances, asynchronous functions could have caused a navigation to fail but expose the     target URL. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.
    (CVE-2021-43536)

  - An incorrect type conversion of sizes from 64bit to 32bit integers allowed an attacker to corrupt memory     leading to a potentially exploitable crash. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR <     91.4.0, and Firefox < 95. (CVE-2021-43537)

  - By misusing a race in our notification code, an attacker could have forcefully hidden the notification for     pages that had received full screen and pointer lock access, which could have been used for spoofing     attacks. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.
    (CVE-2021-43538)

  - Failure to correctly record the location of live pointers across wasm instance calls resulted in a GC     occurring within the call not tracing those live pointers. This could have led to a use-after-free causing     a potentially exploitable crash. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0,     and Firefox < 95. (CVE-2021-43539)

  - WebExtensions with the correct permissions were able to create and install ServiceWorkers for third-party     websites that would not have been uninstalled with the extension. This vulnerability affects Firefox < 95.
    (CVE-2021-43540)

  - When invoking protocol handlers for external protocols, a supplied parameter URL containing spaces was not     properly escaped. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.
    (CVE-2021-43541)

  - Using XMLHttpRequest, an attacker could have identified installed applications by probing error messages     for loading external protocols. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and     Firefox < 95. (CVE-2021-43542)

  - Documents loaded with the CSP sandbox directive could have escaped the sandbox's script restriction by     embedding additional content. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and     Firefox < 95. (CVE-2021-43543)

  - Using the Location API in a loop could have caused severe application hangs and crashes. This     vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95. (CVE-2021-43545)

  - It was possible to recreate previous cursor spoofing attacks against users with a zoomed native cursor.
    This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95. (CVE-2021-43546)

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 92.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2021-38 advisory.

  - Mozilla developers Christian Holler and Lars T Hansen reported memory safety bugs present in Firefox 91.
    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-2021-38494)

  - Firefox for Android allowed navigations through the `intent://` protocol, which could be used to cause     crashes and UI spoofs.  This bug only affects Firefox for Android. Other operating systems are unaffected.
    (CVE-2021-29993)

  - Mixed-content checks were unable to analyze opaque origins which led to some mixed content being loaded.
    (CVE-2021-38491)

  - When delegating navigations to the operating system, Firefox would accept the `mk` scheme which might     allow attackers to launch pages and execute scripts in Internet Explorer in unprivileged mode.  This bug     only affects Firefox for Windows. Other operating systems are unaffected. (CVE-2021-38492)

  - If a domain name contained a RTL character, it would cause the domain to be rendered to the right of the     path. This could lead to user confusion and spoofing attacks.  This bug only affects Firefox for Android.
    Other operating systems are unaffected. Note: Due to a clerical error this advisory was not included in     the original announcement, and was added in February 2022. (CVE-2021-4221)

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 92.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2021-38 advisory.

  - Mozilla developers Christian Holler and Lars T Hansen reported memory safety bugs present in Firefox 91.
    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-2021-38494)

  - Firefox for Android allowed navigations through the `intent://` protocol, which could be used to cause     crashes and UI spoofs.  This bug only affects Firefox for Android. Other operating systems are unaffected.
    (CVE-2021-29993)

  - Mixed-content checks were unable to analyze opaque origins which led to some mixed content being loaded.
    (CVE-2021-38491)

  - When delegating navigations to the operating system, Firefox would accept the `mk` scheme which might     allow attackers to launch pages and execute scripts in Internet Explorer in unprivileged mode.  This bug     only affects Firefox for Windows. Other operating systems are unaffected. (CVE-2021-38492)

  - If a domain name contained a RTL character, it would cause the domain to be rendered to the right of the     path. This could lead to user confusion and spoofing attacks.  This bug only affects Firefox for Android.
    Other operating systems are unaffected. Note: Due to a clerical error this advisory was not included in     the original announcement, and was added in February 2022. (CVE-2021-4221)

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.

  - Mixed-content checks were unable to analyze opaque origins which led to some mixed content being loaded.
    This vulnerability affects Firefox < 92. (CVE-2021-38491)

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

ID	Name	Product	Family	Published	Updated	Severity
404384	Alpine: multiple firefox packages: security update to 92.0.1-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
404384	Alpine: multiple firefox packages: security update to 92.0.1-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	high
426480	Alpine: multiple librewolf packages: security update to 92.0.1-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	5/16/2025	7/2/2026	high
426480	Alpine: multiple librewolf packages: security update to 92.0.1-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	5/16/2025	7/2/2026	high
153183	Ubuntu 18.04 LTS / 20.04 LTS : Firefox vulnerabilities (USN-5074-1)	Nessus	Ubuntu Local Security Checks	9/9/2021	3/6/2025	high
159007	GLSA-202202-03 : Mozilla Firefox: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	3/17/2022	3/6/2025	critical
153088	Mozilla Firefox < 92.0	Nessus	MacOS X Local Security Checks	9/7/2021	12/18/2025	high
153089	Mozilla Firefox < 92.0	Nessus	Windows	9/7/2021	12/18/2025	high
246510	Linux Distros Unpatched Vulnerability : CVE-2021-38491	Nessus	Misc.	8/9/2025	7/28/2026	medium

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