Vulnerability · Published Jul 1, 2026 · Assigned by mozilla
CVE-2026-57963Chat UI manipulation by injection
Medium 6.5
In plain English
A medium-severity cross-site scripting in Thunderbird from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.3%top 76.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | thunderbird | 1:140.13.0esr-2~deb12u1 | DEBIAN-CVE-2026-57963 |
| Debian:13 | thunderbird | 1:140.13.0esr-2~deb13u1 | DEBIAN-CVE-2026-57963 |
| Debian:14 | thunderbird | 1:140.13.0esr-1 | DEBIAN-CVE-2026-57963 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-57963 |
| Ubuntu:24.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-57963 |
| Ubuntu:25.10 | thunderbird | no fix listed | UBUNTU-CVE-2026-57963 |
| Ubuntu:26.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-57963 |
| Ubuntu:26.10 | thunderbird | no fix listed | UBUNTU-CVE-2026-57963 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Thunderbird | see references |
Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N