CVE-2026-0818 — Improper Encoding or Escaping of Output in Mozilla Thunderbird
Severity
4.3MEDIUMNVD
EPSS
0.0%
top 99.49%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
Timeline
PublishedJan 28
Latest updateFeb 2
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, …
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:NExploitability: 2.8 | Impact: 1.4
Affected Packages2 packages
🔴Vulnerability Details
3OSV▶
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 a↗2026-01-28
CVEList▶
CSS-based exfiltration of the content from partially encrypted emails when allowing remote content↗2026-01-28
GHSA▶
GHSA-r27j-r277-j56h: CSS-based exfiltration of the content from partially encrypted emails when allowing remote content↗2026-01-28