CSRF in Mozilla Thunderbird
CVE-2026-0818
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 was fixed in Thunderbird 147.0.1 and Thunderbird 140.7.1.
EPSS: 0.002 (5.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N.
Affected products
- Mozilla Thunderbird — versions 140.7.1, 147.0.1
Weakness classification (CWE)
References
- security@mozilla.org (Permissions Required)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2026-0818?
- CVE-2026-0818 is a medium-severity vulnerability in Mozilla Thunderbird, classified under Improper Encoding or Escaping of Output. CVSS score: 4.3/10. Published 2026-01-28.
- How severe is CVE-2026-0818?
- Medium severity. CVSS v3 base score is 4.3 out of 10.