CVE-2026-84137
Medium
Description
Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
SeverityMedium
CVSS4.3
Exploit probability—
Product
Mozilla Firefox
PublishedSep 1, 2026
First seenSep 1, 2026
Weakness typeCWE-451CWE-451
How to fix
Update
- mozilla firefox153.2.0, 155.0.0 or later
- mozilla thunderbird153.2.0, 155.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 153.2.0, 154.0.0 ≤ v < 155.0.0 | 153.2.0, 155.0.0 |
| mozilla thunderbird | v < 153.2.0, 154.0 ≤ v < 155.0 | 153.2.0, 155.0 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.