Vulnerability record · CVE-2026-57963 · published 1 July 2026

CVE-2026-57963: Mozilla thunderbird cross-site scripting vulnerability

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.

6.5 CVSS 3.1 Medium EPSS 0.31% · top 78.8% CWE-79 · Cross-site scripting

6.5CVSS 3.1 base score

0.31%EPSS exploitation probability, 30 days

NoNot in CISA KEV

1Affected product versions listed by NVD

3References

6 Jul 2026Last modified by NVD

Description

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

Thunderbird Mozilla

References

Link	Tags
https://bugzilla.mozilla.org/show_bug.cgi?id=2042910	Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-63/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-64/	Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-57963), CISA KEV, FIRST EPSS (scores of 2026-10-05). This page is refreshed as NVD updates the record.