CVE-2026-0818— CSS-based exfiltration of the content from partially encrypted emails when allowing remote content
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I. Basic Information for CVE-2026-0818
Vulnerability Information
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Vulnerability Title
CSS-based exfiltration of the content from partially encrypted emails when allowing remote content
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Title
Mozilla Thunderbird 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mozilla Thunderbird是美国Mozilla基金会的一套从Mozilla Application Suite独立出来的电子邮件客户端软件。该软件支持IMAP、POP邮件协议以及HTML邮件格式。 Mozilla Thunderbird 147.0.1之前版本和140.7.1之前版本存在安全漏洞，该漏洞源于允许远程内容时可通过CSS泄露部分加密邮件内容。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mozilla | Thunderbird | 140.7.1 ~ 140.* | - |
II. Public POCs for CVE-2026-0818
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|---|
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IV. Related Vulnerabilities
Same vendor: Mozilla
- CVE-2026-8093
Memory safety bugs fixed in Thunderbird 150.0.2 - CVE-2026-8094
Other issue in the WebRTC component - CVE-2026-8092
Memory safety bugs fixed in Thunderbird ESR 140.10.2 and Thu - CVE-2026-8091
Incorrect boundary conditions in the Audio/Video: Playback c - CVE-2026-8090
Use-after-free in the DOM: Networking component
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