CVE-2026-118174: Displaying a message could load an attacker-chosen URL through an OpenPGP key attachment

Published Oct 27, 2026
·
Updated

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.

Affected Software

2 affected componentsFixes available
Mozilla Thunderbird<159
159
Mozilla Thunderbird<153.6
153.6

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 159
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 153.6
  3. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 159

Event History

Oct 27, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·06:16 PM
Data Sourced
via MITRE·06:16 PM
Description

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

Who is exposed to NTLM credential leakage?

Only Thunderbird users on Windows are exposed to NTLM credential leakage, and only when a displayed message contains a malicious OpenPGP key attachment that points to an attacker-controlled network share. Users on other operating systems can still cause a remote request to be made, but the provided information does not identify NTLM credential leakage on those platforms.

2

Does exploitation require the user to import the attached key or approve a prompt?

No. Thunderbird loaded the external attachment content automatically while displaying the message in order to offer key import, without user interaction.

3

Are systems protected by remote content blocking affected?

Yes. The external attachment load bypassed Thunderbird's remote content blocking, allowing an attacker-chosen URL to be requested when the message was displayed.

4

What version contains the fix?

The issue was fixed in Thunderbird 159.

Company

Resources

Contact

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