When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL header, only the last link is shown when hovering over any attachment. Although the correct link is used on click, the misleading hover text could trick users into downloading content from untrusted sources. This vulnerability affects Thunderbird < 137.0.2 and Thunderbird < 128.9.2.

vendor_unpatched cve-2025-3523: Unpatched CVEs for Debian Linux (cve-2025-3523)

The version of Thunderbird installed on the remote Windows host is prior to 137.0.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-26 advisory.

  - Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be     hosted externally. When an email is opened, Thunderbird accesses the specified URL to  determine file     size, and navigates to it when the user clicks the attachment. Because the URL is not validated or     sanitized, it can reference internal resources like chrome:// or SMB share file:// links, potentially     leading to hashed Windows credential leakage and opening the door to more serious security issues.
    (CVE-2025-3522)

  - By crafting a malformed file name for an attachment in a multipart message, an attacker can trick     Thunderbird into including a directory listing of /tmp when the message is forwarded or edited as a new     message. This vulnerability could allow attackers to disclose sensitive information from the victim's     system. This vulnerability is not limited to Linux; similar behavior has been observed on Windows as well.
    (CVE-2025-2830)

  - When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL     header, only the last link is shown when hovering over any attachment. Although the correct link is used     on click, the misleading hover text could trick users into downloading content from untrusted sources.
    (CVE-2025-3523)

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 137.0.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-26 advisory.

  - Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be     hosted externally. When an email is opened, Thunderbird accesses the specified URL to  determine file     size, and navigates to it when the user clicks the attachment. Because the URL is not validated or     sanitized, it can reference internal resources like chrome:// or SMB share file:// links, potentially     leading to hashed Windows credential leakage and opening the door to more serious security issues.
    (CVE-2025-3522)

  - By crafting a malformed file name for an attachment in a multipart message, an attacker can trick     Thunderbird into including a directory listing of /tmp when the message is forwarded or edited as a new     message. This vulnerability could allow attackers to disclose sensitive information from the victim's     system. This vulnerability is not limited to Linux; similar behavior has been observed on Windows as well.
    (CVE-2025-2830)

  - When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL     header, only the last link is shown when hovering over any attachment. Although the correct link is used     on click, the misleading hover text could trick users into downloading content from untrusted sources.
    (CVE-2025-3523)

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 128.9.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-27 advisory.

  - When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL     header, only the last link is shown when hovering over any attachment. Although the correct link is used     on click, the misleading hover text could trick users into downloading content from untrusted sources.
    (CVE-2025-3523)

  - Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be     hosted externally. When an email is opened, Thunderbird accesses the specified URL to  determine file     size, and navigates to it when the user clicks the attachment. Because the URL is not validated or     sanitized, it can reference internal resources like chrome:// or SMB share file:// links, potentially     leading to hashed Windows credential leakage and opening the door to more serious security issues.
    (CVE-2025-3522)

  - By crafting a malformed file name for an attachment in a multipart message, an attacker can trick     Thunderbird into including a directory listing of /tmp when the message is forwarded or edited as a new     message. This vulnerability could allow attackers to disclose sensitive information from the victim's     system. This vulnerability is not limited to Linux; similar behavior has been observed on Windows as well.
    (CVE-2025-2830)

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 128.9.2. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-27 advisory.

  - When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL     header, only the last link is shown when hovering over any attachment. Although the correct link is used     on click, the misleading hover text could trick users into downloading content from untrusted sources.
    (CVE-2025-3523)

  - Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be     hosted externally. When an email is opened, Thunderbird accesses the specified URL to  determine file     size, and navigates to it when the user clicks the attachment. Because the URL is not validated or     sanitized, it can reference internal resources like chrome:// or SMB share file:// links, potentially     leading to hashed Windows credential leakage and opening the door to more serious security issues.
    (CVE-2025-3522)

  - By crafting a malformed file name for an attachment in a multipart message, an attacker can trick     Thunderbird into including a directory listing of /tmp when the message is forwarded or edited as a new     message. This vulnerability could allow attackers to disclose sensitive information from the victim's     system. This vulnerability is not limited to Linux; similar behavior has been observed on Windows as well.
    (CVE-2025-2830)

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 mozilla-thunderbird installed on the remote host is prior to 128.9.2esr. It is, therefore, affected by multiple vulnerabilities as referenced in the SSA:2025-105-01 advisory.

    New mozilla-thunderbird packages are available for Slackware 15.0 and -current to fix security issues.

Tenable has extracted the preceding description block directly from the mozilla-thunderbird security advisory.

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
234492	Mozilla Thunderbird < 137.0.2	Nessus	Windows	medium
234491	Mozilla Thunderbird < 137.0.2	Nessus	MacOS X Local Security Checks	medium
234457	Mozilla Thunderbird < 128.9.2	Nessus	MacOS X Local Security Checks	medium
234456	Mozilla Thunderbird < 128.9.2	Nessus	Windows	medium
234455	Slackware Linux 15.0 / current mozilla-thunderbird Multiple Vulnerabilities (SSA:2025-105-01)	Nessus	Slackware Local Security Checks	medium

Detections

Analytics

CVE-2025-3523

medium

Tenable Plugins

Coming Soon

medium

medium

medium

medium

medium