CVE-2026-0818

  1. OpenCVE
  2. Vulnerabilities (CVE)
  3. 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.

4.3 /10

CVSS v3 : MEDIUM

V3 Legend

Vector :

Exploitability : 2.8 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References
Link Resource
https://bugzilla.mozilla.org/show_bug.cgi?id=1881530 Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-07/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-08/ Vendor Advisory
https://lists.debian.org/debian-lts-announce/2026/02/msg00005.html
Configurations

Configuration 1 (hide)

OR cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*
History

13 Apr 2026, 15:17

Type Values Removed Values Added
Summary
  • (es) Cuando un usuario solicitó explícitamente a Thunderbird que descifrara un mensaje OpenPGP en línea que estaba incrustado en una sección de texto de un correo electrónico que estaba formateado y estilizado con HTML y CSS, entonces el contenido descifrado se renderizaba en un contexto en el que los estilos CSS de los mensajes externos estaban activos. Si el usuario había permitido adicionalmente la carga del contenido remoto referenciado por el mensaje de correo electrónico externo, y el correo electrónico fue diseñado por el remitente utilizando una combinación de reglas CSS, fuentes y animaciones, entonces era posible extraer el contenido secreto del correo electrónico. Esta vulnerabilidad afecta a Thunderbird < 147.0.1 y Thunderbird < 140.7.1.
Summary (en) 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. (en) 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.

04 Feb 2026, 10:16

Type Values Removed Values Added
References
  • () https://lists.debian.org/debian-lts-announce/2026/02/msg00005.html -

31 Jan 2026, 16:16

Type Values Removed Values Added
Summary (en) 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. (en) 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.

30 Jan 2026, 18:08

Type Values Removed Values Added
First Time Mozilla
Mozilla thunderbird
References () https://bugzilla.mozilla.org/show_bug.cgi?id=1881530 - () https://bugzilla.mozilla.org/show_bug.cgi?id=1881530 - Permissions Required
References () https://www.mozilla.org/security/advisories/mfsa2026-07/ - () https://www.mozilla.org/security/advisories/mfsa2026-07/ - Vendor Advisory
References () https://www.mozilla.org/security/advisories/mfsa2026-08/ - () https://www.mozilla.org/security/advisories/mfsa2026-08/ - Vendor Advisory
CPE cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*

28 Jan 2026, 17:16

Type Values Removed Values Added
CVSS v2 : unknown
v3 : unknown 		v2 : unknown
v3 : 4.3
CWE CWE-200
CWE-352
CWE-116

28 Jan 2026, 08:16

Type Values Removed Values Added
New CVE
Information

Published : 2026-01-28 08:16

Updated : 2026-04-13 15:17

NVD link : CVE-2026-0818

Mitre link : CVE-2026-0818

CVE.ORG link : CVE-2026-0818

JSON object : View

Products Affected

mozilla

  • thunderbird
CWE
CWE-116

Improper Encoding or Escaping of Output

CWE-200

Exposure of Sensitive Information to an Unauthorized Actor

CWE-352

Cross-Site Request Forgery (CSRF)