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. This vulnerability was fixed in Thunderbird 158 and Thunderbird 153.5.

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 macOS or Mac OS X host is prior to 153.5. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-110 advisory.

  - Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158 and     Firefox ESR 153.5. (CVE-2026-109778)

  - Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox     158 and Firefox ESR 153.5. (CVE-2026-109707)

  - 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.

The version of Thunderbird installed on the remote Windows host is prior to 153.5. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-110 advisory.

  - Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 158 and     Firefox ESR 153.5. (CVE-2026-109778)

  - Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox     158 and Firefox ESR 153.5. (CVE-2026-109707)

  - 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
365352	Mozilla Thunderbird < 158.0	Nessus	MacOS X Local Security Checks	Local	critical
365351	Mozilla Thunderbird < 153.5	Nessus	MacOS X Local Security Checks	Local	critical
365350	Mozilla Thunderbird < 158.0	Nessus	Windows	Local	critical
365349	Mozilla Thunderbird < 153.5	Nessus	Windows	Local	critical

Detections

Analytics

CVE-2026-110249

high

Tenable Plugins

critical

critical

critical

critical