Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks. On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent heap allocations. This vulnerability was fixed in Thunderbird 158 and Thunderbird 153.6.

The remote Fedora 45 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-6e46e724e6 advisory.

    Update to latest upstream version.

    ----

    Update to latest upstream version.

Tenable has extracted the preceding description block directly from the Fedora 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 Thunderbird installed on the remote Windows host is prior to 153.6. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-122 advisory.

  - Privilege escalation in the DLL Services component. This vulnerability was fixed in Firefox ESR 153.4,     Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 159, Firefox ESR 153.6, Thunderbird 159,     Thunderbird 153.6, Firefox 157, and Firefox ESR 140.17. (CVE-2026-100801)

  - When a message containing an OpenPGP key attachment was displayed, Thunderbird automatically loaded the     attachment's content to offer importing the key. A sender could mark the attachment as an external     attachment pointing to an arbitrary URL, which Thunderbird then loaded without any user interaction,     bypassing remote content blocking. On Windows, a URL pointing to an attacker-controlled network share     could leak the user's NTLM credentials.  The NTLM credential leak only affects Thunderbird on Windows. On     other operating systems, the issue allowed a remote request that bypassed remote content blocking.
    (CVE-2026-118174)

  - When replying to, forwarding, or editing a crafted email message as new, Thunderbird could embed parts of     a different message stored in the same folder into the message being composed, without showing a blocked     content warning. If the user sent the message, the content of the other message was disclosed to the     recipients. (CVE-2026-118175)

  - Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares     could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause     Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name     and NTLM authentication data, which could be used for offline password cracking or relay attacks.  This     bug only affects Thunderbird on Windows. Other operating systems are unaffected. (CVE-2026-118176)

  - When looking for calendars in a directory on a server, during account setup or when adding a new network     calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network     shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird     subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-     controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's     share or overwrite a local file. (CVE-2026-118177)

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 153.6. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-122 advisory.

  - Privilege escalation in the DLL Services component. This vulnerability was fixed in Firefox ESR 153.4,     Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 159, Firefox ESR 153.6, Thunderbird 159,     Thunderbird 153.6, Firefox 157, and Firefox ESR 140.17. (CVE-2026-100801)

  - When a message containing an OpenPGP key attachment was displayed, Thunderbird automatically loaded the     attachment's content to offer importing the key. A sender could mark the attachment as an external     attachment pointing to an arbitrary URL, which Thunderbird then loaded without any user interaction,     bypassing remote content blocking. On Windows, a URL pointing to an attacker-controlled network share     could leak the user's NTLM credentials.  The NTLM credential leak only affects Thunderbird on Windows. On     other operating systems, the issue allowed a remote request that bypassed remote content blocking.
    (CVE-2026-118174)

  - When replying to, forwarding, or editing a crafted email message as new, Thunderbird could embed parts of     a different message stored in the same folder into the message being composed, without showing a blocked     content warning. If the user sent the message, the content of the other message was disclosed to the     recipients. (CVE-2026-118175)

  - Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares     could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause     Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name     and NTLM authentication data, which could be used for offline password cracking or relay attacks.  This     bug only affects Thunderbird on Windows. Other operating systems are unaffected. (CVE-2026-118176)

  - When looking for calendars in a directory on a server, during account setup or when adding a new network     calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network     shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird     subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-     controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's     share or overwrite a local file. (CVE-2026-118177)

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

The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-cce5679e8f advisory.

    Update to latest upstream version.

Tenable has extracted the preceding description block directly from the Fedora 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.

  - Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks.
    On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated     smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent     heap allocations. This vulnerability was fixed in Thunderbird 158 and Thunderbird 153.6. (CVE-2026-110247)

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

The remote Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-fe87bcd73d advisory.

    Update to latest upstream version.

Tenable has extracted the preceding description block directly from the Fedora 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 Thunderbird installed on the remote macOS or Mac OS X host is prior to 158.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-109 advisory.

  - Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 157.0.1.
    (CVE-2026-106016)

  - Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks.
    On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated     smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent     heap allocations. (CVE-2026-110247)

  - A malicious, compromised, or MITM-controlled Exchange server can return a single well-formed SOAP response     containing an element with enough attributes to keep Thunderbird's main thread CPU-bound for seconds to     hours. (CVE-2026-110249)

  - Privilege escalation in the Application Update component. This vulnerability was fixed in Firefox 158 and     Firefox ESR 153.5. (CVE-2026-109704)

  - Sandbox escape, site isolation issue due to incorrect boundary conditions, use-after-free in the     Networking component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5. (CVE-2026-109705)

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 158.0. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-109 advisory.

  - Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 157.0.1.
    (CVE-2026-106016)

  - Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks.
    On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated     smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent     heap allocations. (CVE-2026-110247)

  - A malicious, compromised, or MITM-controlled Exchange server can return a single well-formed SOAP response     containing an element with enough attributes to keep Thunderbird's main thread CPU-bound for seconds to     hours. (CVE-2026-110249)

  - Privilege escalation in the Application Update component. This vulnerability was fixed in Firefox 158 and     Firefox ESR 153.5. (CVE-2026-109704)

  - Sandbox escape, site isolation issue due to incorrect boundary conditions, use-after-free in the     Networking component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5. (CVE-2026-109705)

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
374606	Fedora 45 : thunderbird (2026-6e46e724e6)	Nessus	Fedora Local Security Checks	Local	critical
372632	Mozilla Thunderbird < 153.6	Nessus	Windows	Local	high
372624	Mozilla Thunderbird < 153.6	Nessus	MacOS X Local Security Checks	Local	high
371729	Fedora 43 : thunderbird (2026-cce5679e8f)	Nessus	Fedora Local Security Checks	Local	critical
369398	Linux Distros Unpatched Vulnerability : CVE-2026-110247	Nessus	Misc.	Local	high
367248	Fedora 44 : thunderbird (2026-fe87bcd73d)	Nessus	Fedora Local Security Checks	Local	critical
365352	Mozilla Thunderbird < 158.0	Nessus	MacOS X Local Security Checks	Local	critical
365350	Mozilla Thunderbird < 158.0	Nessus	Windows	Local	critical

Detections

Analytics

CVE-2026-110247

high

Tenable Plugins

critical

high

high

critical

high

critical

critical

critical