CVE-2026-6771
Critical
Description
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
SeverityCritical
CVSS9.8
Exploit probability—
Product
Mozilla Firefox
PublishedApr 21, 2026
First seenApr 21, 2026
Weakness typeCWE-288CWE-288
How to fix
Update
- mozilla firefox150.0, 140.10.0 or later
- mozilla thunderbird140.10.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 150.0, 140.0 ≤ v < 140.10.0 | 150.0, 140.10.0 |
| mozilla thunderbird | 140.0 ≤ v < 140.10.0 | 140.10.0 |
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