CVE-2026-57963
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HTML Injection in Thunderbird

Publication date: 2026-07-01

Last updated on: 2026-07-06

Assigner: Mozilla Corporation

Description
An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content, phishing links, and CSS that manipulates the chat UI. This vulnerability was fixed in Thunderbird 152.0.1 and Thunderbird 140.12.1.

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Meta Information

Published
2026-07-01
Last Modified
2026-07-06
Generated
2026-07-21
AI Q&A
2026-07-01
EPSS Evaluated
2026-07-20
NVD
CVE-2026-57963
EUVD
EUVD-2026-40862

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
mozilla thunderbird to 140.12.1 (exc)
mozilla thunderbird to 152.0.1 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

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Executive Summary

This vulnerability allows an attacker who can send HTML chat messages via Matrix or XMPP to inject arbitrary styled content, phishing links, and CSS that manipulates the chat user interface.

Impact Analysis

The vulnerability can lead to phishing attacks by injecting malicious links and styled content that can deceive users. It also allows manipulation of the chat UI through CSS, potentially misleading users or hiding malicious activity.

Mitigation Strategies

To mitigate this vulnerability, update Thunderbird to version 152.0.1 or later, or 140.12.1 or later.

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