An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content, phishing links, and CSS that manipulates the chat UI. This vulnerability was fixed in Thunderbird 152.0.1 and Thunderbird 140.12.1.

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

  - An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content,     phishing links, and CSS that manipulates the chat UI. This vulnerability was fixed in Thunderbird 152.0.1     and Thunderbird 140.12.1. (CVE-2026-57963)

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

The version of Thunderbird installed on the remote macOS or Mac OS X host is prior to 140.12.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-64 advisory.

  - An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content,     phishing links, and CSS that manipulates the chat UI. (CVE-2026-57963)

  - A malicious LDAP server, which a Thunderbird user is configured to query for address-book autocomplete,     can stash arbitrarily large amounts of attacker-supplied data into the Thunderbird LDAP client until it     crashes due to memory exhaustion. (CVE-2026-57962)

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 152.0.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-63 advisory.

  - An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content,     phishing links, and CSS that manipulates the chat UI. (CVE-2026-57963)

  - A malicious LDAP server, which a Thunderbird user is configured to query for address-book autocomplete,     can stash arbitrarily large amounts of attacker-supplied data into the Thunderbird LDAP client until it     crashes due to memory exhaustion. (CVE-2026-57962)

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 140.12.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-64 advisory.

  - An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content,     phishing links, and CSS that manipulates the chat UI. (CVE-2026-57963)

  - A malicious LDAP server, which a Thunderbird user is configured to query for address-book autocomplete,     can stash arbitrarily large amounts of attacker-supplied data into the Thunderbird LDAP client until it     crashes due to memory exhaustion. (CVE-2026-57962)

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 152.0.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2026-63 advisory.

  - An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content,     phishing links, and CSS that manipulates the chat UI. (CVE-2026-57963)

  - A malicious LDAP server, which a Thunderbird user is configured to query for address-book autocomplete,     can stash arbitrarily large amounts of attacker-supplied data into the Thunderbird LDAP client until it     crashes due to memory exhaustion. (CVE-2026-57962)

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	Severity
324677	Linux Distros Unpatched Vulnerability : CVE-2026-57963	Nessus	Misc.	medium
324037	Mozilla Thunderbird < 140.12.1	Nessus	MacOS X Local Security Checks	medium
324036	Mozilla Thunderbird < 152.0.1	Nessus	MacOS X Local Security Checks	medium
324035	Mozilla Thunderbird < 140.12.1	Nessus	Windows	medium
324034	Mozilla Thunderbird < 152.0.1	Nessus	Windows	medium

Detections

Analytics

CVE-2026-57963

medium

Tenable Plugins

medium

medium

medium

medium

medium