CVE-2026-57963

Chat UI manipulation by injection

CVSS 6.5 MEDIUMEPSS 0.2%CWE-79

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 6.5EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

01 Jul 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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

Affected products

Mozilla · Thunderbird

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2042910 https://www.mozilla.org/security/advisories/mfsa2026-63/https://www.mozilla.org/security/advisories/mfsa2026-64/