CVE-2026-0818 (GCVE-0-2026-0818)

Vulnerability from cvelistv5 – Published: 2026-01-28 07:39 – Updated: 2026-04-13 13:52
VLAI
Title
CSS-based exfiltration of the content from partially encrypted emails when allowing remote content
Summary
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.
Severity
4.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-352 - Cross-Site Request Forgery (CSRF)
  • CWE-116 - Improper Encoding or Escaping of Output
Assigner
References
Impacted products
Vendor Product Version
Mozilla Thunderbird Unaffected: 140.7.1 , ≤ 140.* (rpm)
Unaffected: 147.0.1 , ≤ * (rpm)
Create a notification for this product.
Credits
Leon Trampert, Daniel Weber, Christian Rossow, Michael Schwarz
Show details on NVD website
To clipboard 

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Sightings

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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