When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If the user had additionally allowed loading of the remote content referenced by the outer email message, and the email was crafted by the sender using a combination of CSS rules and fonts and animations, then it was possible to extract the secret contents of the email. This vulnerability affects Thunderbird < 147.0.1 and Thunderbird < 140.7.1.
Advisories

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Fixes

Solution

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Workaround

No workaround given by the vendor.

History

Sun, 01 Feb 2026 00:30:00 +0900

Type Values Removed Values Added
Description CSS-based exfiltration of the content from partially encrypted emails when allowing remote content. This vulnerability affects Thunderbird < 147.0.1 and Thunderbird < 140.7.1. When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If the user had additionally allowed loading of the remote content referenced by the outer email message, and the email was crafted by the sender using a combination of CSS rules and fonts and animations, then it was possible to extract the secret contents of the email. This vulnerability affects Thunderbird < 147.0.1 and Thunderbird < 140.7.1.

Sat, 31 Jan 2026 03:15:00 +0900

Type Values Removed Values Added
CPEs cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*

Thu, 29 Jan 2026 19:15:00 +0900

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla thunderbird
Vendors & Products Mozilla
Mozilla thunderbird

Thu, 29 Jan 2026 02:15:00 +0900

Type Values Removed Values Added
Weaknesses CWE-116
CWE-200
CWE-352
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 28 Jan 2026 16:45:00 +0900

Type Values Removed Values Added
Description CSS-based exfiltration of the content from partially encrypted emails when allowing remote content. This vulnerability affects Thunderbird < 147.0.1 and Thunderbird < 140.7.1.
Title CSS-based exfiltration of the content from partially encrypted emails when allowing remote content
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-01-31T15:11:09.535Z

Reserved: 2026-01-09T16:32:39.712Z

Link: CVE-2026-0818

cve-icon Vulnrichment

Updated: 2026-01-28T16:49:29.763Z

cve-icon NVD

Status : Modified

Published: 2026-01-28T08:16:03.113

Modified: 2026-01-31T16:16:29.140

Link: CVE-2026-0818

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-01-29T18:18:26Z

Weaknesses