Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid From address to be used. For example, if the From header contains an (invalid) value "Spoofed Name ", Thunderbird treats spoofed@example.com as the actual address. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.

The version of mozilla-thunderbird installed on the remote host is prior to 128.10.1esr. It is, therefore, affected by multiple vulnerabilities as referenced in the SSA:2025-136-01 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.

The remote Debian 12 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-5921 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-5921-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     May 16, 2025                          https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : thunderbird     CVE ID         : CVE-2025-3875 CVE-2025-3877 CVE-2025-3909 CVE-2025-3932

    Multiple security issues were discovered in Thunderbird, which could     result in spoofing of From: mail headers, execution of JavaScript or     information disclosure.

    For the stable distribution (bookworm), these problems have been fixed in     version 1:128.10.1esr-1~deb12u1.

    We recommend that you upgrade your thunderbird packages.

    For the detailed security status of thunderbird please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/thunderbird

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian 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 128.10.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-34 advisory.

  - A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to     the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can     be abused to fill the disk with garbage data (e.g. using /dev/urandom on Linux) or to leak Windows     credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to     download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML     mode is enough to load external content. (CVE-2025-3877)

  - Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid     From address to be used. For example, if the From header contains an (invalid) value Spoofed Name     <spoofed@example.com> <legitimate@example.com>, Thunderbird treats spoofed@example.com as the actual     address. (CVE-2025-3875)

  - Thunderbird's handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute     JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its     content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the     embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-     saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript     execution as part of the HTML. (CVE-2025-3909)

  - It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to     open the attachment, Thunderbird automatically accessed the link. The configuration to block remote     content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in     the X-Mozilla-External-Attachment-URL header of an email. (CVE-2025-3932)

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 128.10.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-34 advisory.

  - A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to     the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can     be abused to fill the disk with garbage data (e.g. using /dev/urandom on Linux) or to leak Windows     credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to     download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML     mode is enough to load external content. (CVE-2025-3877)

  - Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid     From address to be used. For example, if the From header contains an (invalid) value Spoofed Name     <spoofed@example.com> <legitimate@example.com>, Thunderbird treats spoofed@example.com as the actual     address. (CVE-2025-3875)

  - Thunderbird's handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute     JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its     content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the     embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-     saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript     execution as part of the HTML. (CVE-2025-3909)

  - It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to     open the attachment, Thunderbird automatically accessed the link. The configuration to block remote     content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in     the X-Mozilla-External-Attachment-URL header of an email. (CVE-2025-3932)

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 138.0.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-35 advisory.

  - A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to     the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can     be abused to fill the disk with garbage data (e.g. using /dev/urandom on Linux) or to leak Windows     credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to     download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML     mode is enough to load external content. (CVE-2025-3877)

  - Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid     From address to be used. For example, if the From header contains an (invalid) value Spoofed Name     <spoofed@example.com> <legitimate@example.com>, Thunderbird treats spoofed@example.com as the actual     address. (CVE-2025-3875)

  - Thunderbird's handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute     JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its     content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the     embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-     saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript     execution as part of the HTML. (CVE-2025-3909)

  - It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to     open the attachment, Thunderbird automatically accessed the link. The configuration to block remote     content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in     the X-Mozilla-External-Attachment-URL header of an email. (CVE-2025-3932)

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 138.0.1. It is, therefore, affected by multiple vulnerabilities as referenced in the mfsa2025-35 advisory.

  - A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to     the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can     be abused to fill the disk with garbage data (e.g. using /dev/urandom on Linux) or to leak Windows     credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to     download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML     mode is enough to load external content. (CVE-2025-3877)

  - Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid     From address to be used. For example, if the From header contains an (invalid) value Spoofed Name     <spoofed@example.com> <legitimate@example.com>, Thunderbird treats spoofed@example.com as the actual     address. (CVE-2025-3875)

  - Thunderbird's handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute     JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its     content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the     embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-     saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript     execution as part of the HTML. (CVE-2025-3909)

  - It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to     open the attachment, Thunderbird automatically accessed the link. The configuration to block remote     content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in     the X-Mozilla-External-Attachment-URL header of an email. (CVE-2025-3932)

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
236882	Slackware Linux 15.0 / current mozilla-thunderbird Multiple Vulnerabilities (SSA:2025-136-01)	Nessus	Slackware Local Security Checks	high
236871	Debian dsa-5921 : thunderbird - security update	Nessus	Debian Local Security Checks	high
236405	Mozilla Thunderbird < 128.10.1	Nessus	MacOS X Local Security Checks	medium
236404	Mozilla Thunderbird < 128.10.1	Nessus	Windows	medium
236403	Mozilla Thunderbird < 138.0.1	Nessus	MacOS X Local Security Checks	medium
236402	Mozilla Thunderbird < 138.0.1	Nessus	Windows	medium

Detections

Analytics

CVE-2025-3875

high

Tenable Plugins

high

high

medium

medium

medium

medium