CVE-2026-0818
thunderbird - security update
Description
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.
How to fix CVE-2026-0818
To remediate CVE-2026-0818, upgrade the affected package to a fixed version below.
- —upgrade to 1:140.7.1esr-1~deb11u1 or later
- —upgrade to 1:140.7.1esr-1~deb11u1 or later
- —upgrade to 1:140.7.1esr-1~deb12u1 or later
Is CVE-2026-0818 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- from 0, < 1:140.7.1esr-1~deb11u1
- from 0, < 1:140.7.1esr-1~deb11u1
- from 0, < 1:140.7.1esr-1~deb12u1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM4.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N |