The remote CentOS Linux 7 host has a package installed that is affected by multiple vulnerabilities as referenced in the RHSA-2021:4116 advisory.

  - 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)

  - Mozilla developers and community members reported memory safety bugs present in Firefox 93 and Firefox ESR     91.2. 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 < 94,     Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-43534)

  - A use-after-free could have occured when an HTTP2 session object was released on a different thread,     leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 93,     Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-43535)

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

The remote SUSE Linux SLED15 / SLES15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2021:4150-1 advisory.

  - 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)

  - 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 accepted a newline in a HTTP/3 header, interpretting it as two separate headers. This     allowed for a header splitting attack against servers using HTTP/3. This vulnerability affects Firefox <     91.0.1 and Thunderbird < 91.0.1. (CVE-2021-29991)

  - crossbeam-deque is a package of work-stealing deques for building task schedulers when programming in     Rust. In versions prior to 0.7.4 and 0.8.0, the result of the race condition is that one or more tasks in     the worker queue can be popped twice instead of other tasks that are forgotten and never popped. If tasks     are allocated on the heap, this can cause double free and a memory leak. If not, this still can cause a     logical bug. Crates using `Stealer::steal`, `Stealer::steal_batch`, or `Stealer::steal_batch_and_pop` are     affected by this issue. This has been fixed in crossbeam-deque 0.8.1 and 0.7.4. (CVE-2021-32810)

  - 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.*. This vulnerability affects     Firefox < 92, Thunderbird < 91.1, Thunderbird < 78.14, Firefox ESR < 78.14, and Firefox ESR < 91.1.
    (CVE-2021-38492)

  - 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)

  - During operations on MessageTasks, a task may have been removed while it was still scheduled, resulting in     memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.15,     Thunderbird < 91.2, Firefox ESR < 91.2, Firefox ESR < 78.15, and Firefox < 93. (CVE-2021-38496)

  - Through use of reportValidity() and window.open(), a plain-text validation message could have been     overlaid on another origin, leading to possible user confusion and spoofing attacks. This vulnerability     affects Firefox < 93, Thunderbird < 91.2, and Firefox ESR < 91.2. (CVE-2021-38497)

  - During process shutdown, a document could have caused a use-after-free of a languages service object,     leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 93,     Thunderbird < 91.2, and Firefox ESR < 91.2. (CVE-2021-38498)

  - Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1. 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 Thunderbird < 78.15, Thunderbird < 91.2,     Firefox ESR < 91.2, Firefox ESR < 78.15, and Firefox < 93. (CVE-2021-38500)

  - Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1. 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 < 93, Thunderbird < 91.2, and     Firefox ESR < 91.2. (CVE-2021-38501)

  - Thunderbird ignored the configuration to require STARTTLS security for an SMTP connection. A MITM could     perform a downgrade attack to intercept transmitted messages, or could take control of the authenticated     session to execute SMTP commands chosen by the MITM. If an unprotected authentication method was     configured, the MITM could obtain the authentication credentials, too. This vulnerability affects     Thunderbird < 91.2. (CVE-2021-38502)

  - 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)

  - Microsoft introduced a new feature in Windows 10 known as Cloud Clipboard which, if enabled, will record     data copied to the clipboard to the cloud, and make it available on other computers in certain scenarios.
    Applications that wish to prevent copied data from being recorded in Cloud History must use specific     clipboard formats; and Firefox before versions 94 and ESR 91.3 did not implement them. This could have     caused sensitive data to be recorded to a user's Microsoft account. *This bug only affects Firefox for     Windows 10+ with Cloud Clipboard enabled. Other operating systems are unaffected.*. This vulnerability     affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3. (CVE-2021-38505)

  - 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)

  - The executable file warning was not presented when downloading .inetloc files, which, due to a flaw in Mac     OS, can run commands on a user's computer.*Note: This issue only affected Mac OS operating systems. Other     operating systems are unaffected.*. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and     Firefox ESR < 91.3. (CVE-2021-38510)

  - The ElGamal implementation in Botan through 2.18.1, as used in Thunderbird and other products, allows     plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous     combination of the prime defined by the receiver's public key, the generator defined by the receiver's     public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.
    (CVE-2021-40529)

  - Thunderbird unexpectedly enabled JavaScript in the composition area. The JavaScript execution context was     limited to this area and did not receive chrome-level privileges, but could be used as a stepping stone to     further an attack with other vulnerabilities. This vulnerability affects Thunderbird < 91.4.0.
    (CVE-2021-43528)

  - 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)

  - 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 these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-5248-1 advisory.

    Multiple security issues were discovered in Thunderbird. If a user were tricked into opening a specially     crafted website in a browsing context, an attacker could potentially exploit these to cause a denial of     service, obtain sensitive information, trick a user into accepting unwanted permissions, conduct header     splitting attacks, conduct spoofing attacks, bypass security restrictions, confuse the user, or execute     arbitrary code. (CVE-2021-4129, CVE-2021-4140, CVE-2021-29981, CVE-2021-29982, CVE-2021-29987,     CVE-2021-29991, CVE-2021-38495, CVE-2021-38496, CVE-2021-38497, CVE-2021-38498, CVE-2021-38500,     CVE-2021-38501, CVE-2021-38503, CVE-2021-38504, CVE-2021-38506, CVE-2021-38507, CVE-2021-38508,     CVE-2021-38509, CVE-2021-43534, CVE-2021-43535, CVE-2021-43536, CVE-2021-43537, CVE-2021-43538,     CVE-2021-43539, CVE-2021-43541, CVE-2021-43542, CVE-2021-43543, CVE-2021-43545, CVE-2021-43656,     CVE-2022-22737, CVE-2022-22738, CVE-2022-22739, CVE-2022-22740, CVE-2022-22741, CVE-2022-22742,     CVE-2022-22743, CVE-2022-22745, CVE-2022-22747, CVE-2022-22748, CVE-2022-22751)

    It was discovered that Thunderbird ignored the configuration to require STARTTLS for an SMTP connection. A     person-in-the-middle could potentially exploit this to perform a downgrade attack in order to intercept     messages or take control of a session. (CVE-2021-38502)

    It was discovered that JavaScript was unexpectedly enabled in the composition area. An attacker could     potentially exploit this in combination with another vulnerability, with unspecified impacts.
    (CVE-2021-43528)

    A buffer overflow was discovered in the Matrix chat library bundled with Thunderbird. An attacker could     potentially exploit this to cause a denial of service, or execute arbitrary code. (CVE-2021-44538)

    It was discovered that Thunderbird's OpenPGP integration only considered the inner signed message when     checking signature validity in a message that contains an additional outer MIME layer. An attacker could     potentially exploit this to trick the user into thinking that a message has a valid signature.
    (CVE-2021-4126)

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

  - 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)

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

ID	名稱	產品	系列	已發布	已更新	嚴重性
155539	CentOS 7 : firefox (RHSA-2021:4116)	Nessus	CentOS Local Security Checks	2021/11/17	2024/10/9	critical
156292	SUSE SLED15 / SLES15 Security Update : MozillaThunderbird (SUSE-SU-2021:4150-1)	Nessus	SuSE Local Security Checks	2021/12/25	2025/3/6	critical
156961	Ubuntu 18.04 LTS / 20.04 LTS : Thunderbird vulnerabilities (USN-5248-1)	Nessus	Ubuntu Local Security Checks	2022/1/22	2025/3/6	critical
249869	Linux Distros Unpatched Vulnerability : CVE-2021-38507	Nessus	Misc.	2025/8/15	2025/8/15	medium

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