CVE-2026-57963: Vulnerability in Mozilla Thunderbird
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.
AI Analysis
Technical Summary
The vulnerability CVE-2026-57963 in Mozilla Thunderbird enables 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. This issue is related to improper handling of HTML content in the chat feature, classified under CWE-79 (Cross-site Scripting). The vulnerability was addressed and fixed in Thunderbird versions 140.12.1 and 152.0.1. Exploitation through email is not feasible due to scripting restrictions in mail reading, but the risk exists in browser or browser-like contexts within the application.
Potential Impact
Successful exploitation allows an attacker to manipulate the chat UI by injecting styled content and phishing links, potentially misleading users and facilitating phishing attacks. The impact is limited to the chat interface and does not affect email reading due to scripting being disabled there. The CVSS score is 6.5 (medium severity), reflecting the potential for limited confidentiality and integrity impact without availability impact.
Mitigation Recommendations
This vulnerability has been fixed in Mozilla Thunderbird versions 140.12.1 and 152.0.1. Users and administrators should upgrade affected Thunderbird installations to at least these versions to remediate the issue. Since the vendor advisory confirms the fix, no additional mitigation steps are required beyond applying the official update.
CVE-2026-57963: Vulnerability in Mozilla Thunderbird
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.
CVSS v3.1
Score 6.5medium
Affected software
pkg:github/mozilla/thunderbirdRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability CVE-2026-57963 in Mozilla Thunderbird enables 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. This issue is related to improper handling of HTML content in the chat feature, classified under CWE-79 (Cross-site Scripting). The vulnerability was addressed and fixed in Thunderbird versions 140.12.1 and 152.0.1. Exploitation through email is not feasible due to scripting restrictions in mail reading, but the risk exists in browser or browser-like contexts within the application.
Potential Impact
Successful exploitation allows an attacker to manipulate the chat UI by injecting styled content and phishing links, potentially misleading users and facilitating phishing attacks. The impact is limited to the chat interface and does not affect email reading due to scripting being disabled there. The CVSS score is 6.5 (medium severity), reflecting the potential for limited confidentiality and integrity impact without availability impact.
Mitigation Recommendations
This vulnerability has been fixed in Mozilla Thunderbird versions 140.12.1 and 152.0.1. Users and administrators should upgrade affected Thunderbird installations to at least these versions to remediate the issue. Since the vendor advisory confirms the fix, no additional mitigation steps are required beyond applying the official update.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-06-26T15:27:32.832Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2026-62/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-63/","vendor":"Mozilla"}]
Threat ID: 6a446bac27e9c79719c2438f
Added to database: 07/01/2026, 01:21:48 UTC
Last enriched: 07/08/2026, 12:49:37 UTC
Last updated: 08/11/2026, 00:41:13 UTC
Views: 102
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